1.修改BCD的写入和读取方式

2.增加日期有针对性的写入和读取方式

src/JT808.Protocol.Test/MessagePack/JT808MessagePackWriterTest.cs

@@ -509,5 +509,46 @@ namespace JT808.Protocol.Test.MessagePack
             var hex = msgpackWriter.FlushAndGetEncodingArray().ToHexString();
             Assert.Equal("736D616C6C636869286B6F696B652900", hex);
         }
+
+        [Fact]
+        public void IntToBcdTest()
+        {
+            var bytes1 = new byte[5];
+            Span<byte> buffer1 = new Span<byte>(bytes1);
+            IntToBcd(123456700, buffer1, buffer1.Length);
+            Assert.NotEqual(new byte[] { 0x12, 0x34, 0x56, 0x70,0x00 }, buffer1.ToArray());
+            Assert.Equal(new byte[] { 0x01, 0x23, 0x45, 0x67,0x00 }, buffer1.ToArray());
+
+            var bytes = new byte[6];
+            Span<byte> buffer = new Span<byte>(bytes);
+            IntToBcd(123456700, buffer, buffer.Length);
+            Assert.Equal(new byte[] { 0x00, 0x01, 0x23, 0x45, 0x67, 0x00 }, buffer.ToArray());
+        }
+
+        [Fact]
+        public void WriteBcdTest()
+        {
+            byte[] array = new byte[100];
+            var msgpackWriter = new JT808MessagePackWriter(array);
+            int val1 = 1234567890;
+            long val2 = 123456789011;
+            msgpackWriter.WriteBCD(val1, 5);
+            msgpackWriter.WriteBCD(val2, 10);
+            var result = msgpackWriter.FlushAndGetRealArray();
+            Assert.Equal(new byte[] { 0x12, 0x34, 0x56, 0x78, 0x90, 0x00, 0x00, 0x00, 0x00, 0x12, 0x34, 0x56, 0x78, 0x90, 0x11 }, result);
+        }
+
+        private void IntToBcd(int num, Span<byte> list, int count)
+        {
+            int level = count - 1;
+            var high = num / 100;
+            var low = num % 100;
+            if (high > 0)
+            {
+                IntToBcd(high, list, --count);
+            }
+            byte res = (byte)(((low / 10) << 4) + (low % 10));
+            list[level] = res;
+        }
     }
 }

src/JT808.Protocol/JT808.Protocol.xml

@@ -18256,48 +18256,95 @@
             </summary>
             <param name="format">>D2： 10  X2：16</param>
         </member>
+        <member name="M:JT808.Protocol.MessagePack.JT808MessagePackReader.ReadDateTime_yyMMddHHmmss">
+            <summary>
+            读取六字节日期,yyMMddHHmmss
+            </summary>
+        </member>
+        <member name="M:JT808.Protocol.MessagePack.JT808MessagePackReader.BcdToInt(System.Byte)">
+            <summary>
+            16进制的BCD BYTE转成整型
+            </summary>
+            <param name="value">16进制的BCD BYTE转成整型</param>
+            <returns></returns>
+        </member>
         <member name="M:JT808.Protocol.MessagePack.JT808MessagePackReader.ReadDateTimeNull6(System.String)">
             <summary>
             读取可空类型的六字节日期,yyMMddHHmmss
             </summary>
             <param name="format">>D2： 10  X2：16</param>
         </member>
+        <member name="M:JT808.Protocol.MessagePack.JT808MessagePackReader.ReadDateTimeNull_yyMMddHHmmss">
+            <summary>
+            读取可空类型的六字节日期,yyMMddHHmmss
+            </summary>
+        </member>
         <member name="M:JT808.Protocol.MessagePack.JT808MessagePackReader.ReadDateTime5(System.String)">
             <summary>
             读取五字节日期,HH-mm-ss-msms|HH-mm-ss-fff
             </summary>
             <param name="format">D2： 10  X2：16</param>
         </member>
+        <member name="M:JT808.Protocol.MessagePack.JT808MessagePackReader.ReadDateTime_HHmmssfff">
+            <summary>
+            读取五字节日期,HH-mm-ss-msms|HH-mm-ss-fff
+            </summary>
+        </member>
         <member name="M:JT808.Protocol.MessagePack.JT808MessagePackReader.ReadDateTimeNull5(System.String)">
             <summary>
             读取可空类型的五字节日期,HH-mm-ss-msms|HH-mm-ss-fff
             </summary>
             <param name="format">D2： 10  X2：16</param>
         </member>
+        <member name="M:JT808.Protocol.MessagePack.JT808MessagePackReader.ReadDateTimeNull_HHmmssfff">
+            <summary>
+            读取可空类型的五字节日期,HH-mm-ss-msms|HH-mm-ss-fff
+            </summary>
+        </member>
         <member name="M:JT808.Protocol.MessagePack.JT808MessagePackReader.ReadDateTime4(System.String)">
             <summary>
             读取四字节日期，YYYYMMDD
             </summary>
             <param name="format">D2： 10  X2：16</param>
         </member>
+        <member name="M:JT808.Protocol.MessagePack.JT808MessagePackReader.ReadDateTime_YYYYMMDD">
+            <summary>
+            读取四字节日期，YYYYMMDD
+            </summary>
+        </member>
         <member name="M:JT808.Protocol.MessagePack.JT808MessagePackReader.ReadDateTimeNull4(System.String)">
             <summary>
             读取可空类型的四字节日期，YYYYMMDD
             </summary>
             <param name="format">D2： 10  X2：16</param>
         </member>
+        <member name="M:JT808.Protocol.MessagePack.JT808MessagePackReader.ReadDateTimeNull_YYYYMMDD">
+            <summary>
+            读取可空类型的四字节日期，YYYYMMDD
+            </summary>
+        </member>
         <member name="M:JT808.Protocol.MessagePack.JT808MessagePackReader.ReadDateTime3(System.String)">
             <summary>
             读取三字节日期，YYMMDD
             </summary>
             <param name="format">D2： 10  X2：16</param>
         </member>
+        <member name="M:JT808.Protocol.MessagePack.JT808MessagePackReader.ReadDateTime_YYMMDD">
+            <summary>
+            读取三字节日期，YYMMDD
+            </summary>
+        </member>
         <member name="M:JT808.Protocol.MessagePack.JT808MessagePackReader.ReadDateTimeNull3(System.String)">
             <summary>
             读取可空类型的三字节日期，YYMMDD
             </summary>
             <param name="format">D2： 10  X2：16</param>
         </member>
+        <member name="M:JT808.Protocol.MessagePack.JT808MessagePackReader.ReadDateTimeNull_YYMMDD">
+            <summary>
+            读取可空类型的三字节日期，YYMMDD
+            </summary>
+        </member>
         <member name="M:JT808.Protocol.MessagePack.JT808MessagePackReader.ReadUTCDateTime">
             <summary>
             读取UTC时间类型
@@ -18567,6 +18614,45 @@
             <param name="src"></param>
             <param name="position"></param>
         </member>
+        <member name="M:JT808.Protocol.MessagePack.JT808MessagePackWriter.IntToBcd(System.Int32)">
+            <summary>
+            整型数据转为BCD BYTE
+            为了兼容int类型，不使用byte做参数
+            支持0xFF一个字节的转换
+            </summary>
+            <param name="value"></param>
+            <returns></returns>
+        </member>
+        <member name="M:JT808.Protocol.MessagePack.JT808MessagePackWriter.IntToBcd(System.Int32,System.Span{System.Byte},System.Int32)">
+            <summary>
+            整型数据转为BCD BYTE[]
+            </summary>
+            <param name="value">整数值</param>
+            <param name="list">bytes</param>
+            <param name="count">字节数>=整数值</param>
+        </member>
+        <member name="M:JT808.Protocol.MessagePack.JT808MessagePackWriter.IntToBcd(System.Int64,System.Span{System.Byte},System.Int32)">
+            <summary>
+            整型数据转为BCD BYTE[]
+            </summary>
+            <param name="value">整数值</param>
+            <param name="list">bytes</param>
+            <param name="byteCount">字节数>=整数值</param>
+        </member>
+        <member name="M:JT808.Protocol.MessagePack.JT808MessagePackWriter.WriteBCD(System.Int64@,System.Int32@)">
+            <summary>
+            写入BCD编码数据
+            </summary>
+            <param name="value">整数值</param>
+            <param name="byteCount">字节数>=整数值</param>
+        </member>
+        <member name="M:JT808.Protocol.MessagePack.JT808MessagePackWriter.WriteBCD(System.Int32@,System.Int32@)">
+            <summary>
+            写入BCD编码数据
+            </summary>
+            <param name="value">整数值</param>
+            <param name="count">字节数>=整数值</param>
+        </member>
         <member name="M:JT808.Protocol.MessagePack.JT808MessagePackWriter.WriteDateTime6(System.DateTime@,System.Int32@)">
             <summary>
             写入六个字节的日期类型,yyMMddHHmmss
@@ -18574,6 +18660,12 @@
             <param name="value"></param>
             <param name="fromBase"></param>
         </member>
+        <member name="M:JT808.Protocol.MessagePack.JT808MessagePackWriter.WriteDateTime_yyMMddHHmmss(System.DateTime@)">
+            <summary>
+            写入六个字节的日期类型,yyMMddHHmmss
+            </summary>
+            <param name="value"></param>
+        </member>
         <member name="M:JT808.Protocol.MessagePack.JT808MessagePackWriter.WriteDateTime6(System.Nullable{System.DateTime}@,System.Int32@)">
             <summary>
             写入六个字节的可空日期类型,yyMMddHHmmss
@@ -18581,6 +18673,12 @@
             <param name="value"></param>
             <param name="fromBase"></param>
         </member>
+        <member name="M:JT808.Protocol.MessagePack.JT808MessagePackWriter.WriteDateTime_yyMMddHHmmss(System.Nullable{System.DateTime}@)">
+            <summary>
+            写入六个字节的可空日期类型,yyMMddHHmmss
+            </summary>
+            <param name="value"></param>
+        </member>
         <member name="M:JT808.Protocol.MessagePack.JT808MessagePackWriter.WriteDateTime5(System.DateTime@,System.Int32@)">
             <summary>
             写入五个字节的日期类型,HH-mm-ss-msms或HH-mm-ss-fff
@@ -18588,6 +18686,12 @@
             <param name="value"></param>
             <param name="fromBase"></param>
         </member>
+        <member name="M:JT808.Protocol.MessagePack.JT808MessagePackWriter.WriteDateTime_HHmmssfff(System.DateTime@)">
+            <summary>
+            写入五个字节的日期类型,HH-mm-ss-msms或HH-mm-ss-fff
+            </summary>
+            <param name="value"></param>
+        </member>
         <member name="M:JT808.Protocol.MessagePack.JT808MessagePackWriter.WriteDateTime5(System.Nullable{System.DateTime}@,System.Int32@)">
             <summary>
             写入五个字节的可空日期类型,HH-mm-ss-msms或HH-mm-ss-fff
@@ -18595,6 +18699,12 @@
             <param name="value"></param>
             <param name="fromBase"></param>
         </member>
+        <member name="M:JT808.Protocol.MessagePack.JT808MessagePackWriter.WriteDateTime_HHmmssfff(System.Nullable{System.DateTime}@)">
+            <summary>
+            写入五个字节的可空日期类型,HH-mm-ss-msms或HH-mm-ss-fff
+            </summary>
+            <param name="value"></param>
+        </member>
         <member name="M:JT808.Protocol.MessagePack.JT808MessagePackWriter.WriteUTCDateTime(System.DateTime@)">
             <summary>
             写入UTC日期类型
@@ -18608,6 +18718,12 @@
             <param name="value"></param>
             <param name="fromBase"></param>
         </member>
+        <member name="M:JT808.Protocol.MessagePack.JT808MessagePackWriter.WriteDateTime_YYYYMMDD(System.DateTime@)">
+            <summary>
+            写入四个字节的日期类型,YYYYMMDD BCD[4] 数据形如：20200101
+            </summary>
+            <param name="value"></param>
+        </member>
         <member name="M:JT808.Protocol.MessagePack.JT808MessagePackWriter.WriteDateTime4(System.Nullable{System.DateTime}@,System.Int32@)">
             <summary>
             写入四个字节的可空日期类型,YYYYMMDD BCD[4]数据形如:20200101
@@ -18615,6 +18731,12 @@
             <param name="value"></param>
             <param name="fromBase"></param>
         </member>
+        <member name="M:JT808.Protocol.MessagePack.JT808MessagePackWriter.WriteDateTime_YYYYMMDD(System.Nullable{System.DateTime}@)">
+            <summary>
+            写入四个字节的可空日期类型,YYYYMMDD BCD[4]数据形如:20200101
+            </summary>
+            <param name="value"></param>
+        </member>
         <member name="M:JT808.Protocol.MessagePack.JT808MessagePackWriter.WriteDateTime3(System.DateTime@,System.Int32@)">
             <summary>
             写入三个字节的日期类型,YYMMDD 数据形如：20200101
@@ -18622,6 +18744,12 @@
             <param name="value"></param>
             <param name="fromBase"></param>
         </member>
+        <member name="M:JT808.Protocol.MessagePack.JT808MessagePackWriter.WriteDateTime_YYMMDD(System.DateTime@)">
+            <summary>
+            写入三个字节的日期类型,YYMMDD 数据形如：20200101
+            </summary>
+            <param name="value"></param>
+        </member>
         <member name="M:JT808.Protocol.MessagePack.JT808MessagePackWriter.WriteDateTime3(System.Nullable{System.DateTime}@,System.Int32@)">
             <summary>
             写入三个字节的可空日期类型,YYMMDD 数据形如：20200101
@@ -18629,6 +18757,12 @@
             <param name="value"></param>
             <param name="fromBase"></param>
         </member>
+        <member name="M:JT808.Protocol.MessagePack.JT808MessagePackWriter.WriteDateTime_YYMMDD(System.Nullable{System.DateTime}@)">
+            <summary>
+            写入三个字节的可空日期类型,YYMMDD 数据形如：20200101
+            </summary>
+            <param name="value"></param>
+        </member>
         <member name="M:JT808.Protocol.MessagePack.JT808MessagePackWriter.WriteXor(System.Int32@,System.Int32@)">
             <summary>
             将指定内存块进行或运算并写入一个字节

src/JT808.Protocol/MessagePack/JT808MessagePackReader.cs

@@ -371,18 +371,19 @@ namespace JT808.Protocol.MessagePack
         /// 读取六字节日期,yyMMddHHmmss
         /// </summary>
         /// <param name="format">>D2： 10  X2：16</param>
+        [Obsolete("use ReadDateTime_yyMMddHHmmss")]
         public DateTime ReadDateTime6(string format = "X2")
         {
             DateTime d;
             try
             {
                 var readOnlySpan = GetReadOnlySpan(6);
-                int year = Convert.ToInt32(readOnlySpan[0].ToString(format)) + JT808Constants.DateLimitYear;
-                int month = Convert.ToInt32(readOnlySpan[1].ToString(format));
-                int day = Convert.ToInt32(readOnlySpan[2].ToString(format));
-                int hour = Convert.ToInt32(readOnlySpan[3].ToString(format));
-                int minute = Convert.ToInt32(readOnlySpan[4].ToString(format));
-                int second = Convert.ToInt32(readOnlySpan[5].ToString(format));
+                int year = BcdToInt(readOnlySpan[0])  + JT808Constants.DateLimitYear;
+                int month = BcdToInt(readOnlySpan[1]);
+                int day = BcdToInt(readOnlySpan[2]);
+                int hour = BcdToInt(readOnlySpan[3]);
+                int minute = BcdToInt(readOnlySpan[4]);
+                int second = BcdToInt(readOnlySpan[5]);
                 d = new DateTime(year, month, day, hour, minute, second);
             }
             catch (Exception)
@@ -392,21 +393,81 @@ namespace JT808.Protocol.MessagePack
             return d;
         }
         /// <summary>
+        /// 读取六字节日期,yyMMddHHmmss
+        /// </summary>
+        public DateTime ReadDateTime_yyMMddHHmmss()
+        {
+            DateTime d;
+            try
+            {
+                var readOnlySpan = GetReadOnlySpan(6);
+                int year = BcdToInt(readOnlySpan[0]) + JT808Constants.DateLimitYear;
+                int month = BcdToInt(readOnlySpan[1]);
+                int day = BcdToInt(readOnlySpan[2]);
+                int hour = BcdToInt(readOnlySpan[3]);
+                int minute = BcdToInt(readOnlySpan[4]);
+                int second = BcdToInt(readOnlySpan[5]);
+                d = new DateTime(year, month, day, hour, minute, second);
+            }
+            catch (Exception)
+            {
+                d = JT808Constants.UTCBaseTime;
+            }
+            return d;
+        }
+        /// <summary>
+        /// 16进制的BCD BYTE转成整型
+        /// </summary>
+        /// <param name="value">16进制的BCD BYTE转成整型</param>
+        /// <returns></returns>
+        public int BcdToInt(byte value)
+        {
+            int high = value >> 4;
+            int low = value & 0xF;
+            int number = 10 * high + low;
+            return number;
+        }
+        /// <summary>
         /// 读取可空类型的六字节日期,yyMMddHHmmss
         /// </summary>
         /// <param name="format">>D2： 10  X2：16</param>
+        [Obsolete("use ReadDateTimeNull_yyMMddHHmmss")]
         public DateTime? ReadDateTimeNull6(string format = "X2")
         {
             DateTime? d;
             try
             {
                 var readOnlySpan = GetReadOnlySpan(6);
-                int year = Convert.ToInt32(readOnlySpan[0].ToString(format)) ;
-                int month = Convert.ToInt32(readOnlySpan[1].ToString(format));
-                int day = Convert.ToInt32(readOnlySpan[2].ToString(format));
-                int hour = Convert.ToInt32(readOnlySpan[3].ToString(format));
-                int minute = Convert.ToInt32(readOnlySpan[4].ToString(format));
-                int second = Convert.ToInt32(readOnlySpan[5].ToString(format));
+                int year = BcdToInt(readOnlySpan[0]);
+                int month = BcdToInt(readOnlySpan[1]);
+                int day = BcdToInt(readOnlySpan[2]);
+                int hour = BcdToInt(readOnlySpan[3]);
+                int minute = BcdToInt(readOnlySpan[4]);
+                int second = BcdToInt(readOnlySpan[5]);
+                if (year == 0 && month == 0 && day == 0 && hour == 0 && minute == 0 && second == 0) return null;
+                d = new DateTime(year + JT808Constants.DateLimitYear, month, day, hour, minute, second);
+            }
+            catch (Exception)
+            {
+                return null;
+            }
+            return d;
+        }
+        /// <summary>
+        /// 读取可空类型的六字节日期,yyMMddHHmmss
+        /// </summary>
+        public DateTime? ReadDateTimeNull_yyMMddHHmmss()
+        {
+            DateTime? d;
+            try
+            {
+                var readOnlySpan = GetReadOnlySpan(6);
+                int year = BcdToInt(readOnlySpan[0]);
+                int month = BcdToInt(readOnlySpan[1]);
+                int day = BcdToInt(readOnlySpan[2]);
+                int hour = BcdToInt(readOnlySpan[3]);
+                int minute = BcdToInt(readOnlySpan[4]);
+                int second = BcdToInt(readOnlySpan[5]);
                 if (year == 0 && month == 0 && day == 0 && hour == 0 && minute == 0 && second == 0) return null;
                 d = new DateTime(year + JT808Constants.DateLimitYear, month, day, hour, minute, second);
             }
@@ -420,23 +481,45 @@ namespace JT808.Protocol.MessagePack
         /// 读取五字节日期,HH-mm-ss-msms|HH-mm-ss-fff
         /// </summary>
         /// <param name="format">D2： 10  X2：16</param>
+        [Obsolete("use ReadDateTime_HHmmssfff")]
         public DateTime ReadDateTime5(string format = "X2")
         {
             DateTime d;
             try
             {
                 var readOnlySpan = GetReadOnlySpan(5);
-                StringBuilder sb = new StringBuilder(4);
-                sb.Append(readOnlySpan[3].ToString(format));
-                sb.Append(readOnlySpan[4].ToString(format));
+                var fff = BcdToInt(readOnlySpan[3]) * 100 + BcdToInt(readOnlySpan[4]);
+                d = new DateTime(
+                DateTime.Now.Year,
+                DateTime.Now.Month,
+                DateTime.Now.Day,
+                BcdToInt(readOnlySpan[0]),
+                BcdToInt(readOnlySpan[1]),
+                BcdToInt(readOnlySpan[2]), fff);
+            }
+            catch
+            {
+                d = JT808Constants.UTCBaseTime;
+            }
+            return d;
+        }
+        /// <summary>
+        /// 读取五字节日期,HH-mm-ss-msms|HH-mm-ss-fff
+        /// </summary>
+        public DateTime ReadDateTime_HHmmssfff()
+        {
+            DateTime d;
+            try
+            {
+                var readOnlySpan = GetReadOnlySpan(5);
+                var fff = BcdToInt(readOnlySpan[3]) * 100 + BcdToInt(readOnlySpan[4]);
                 d = new DateTime(
                 DateTime.Now.Year,
                 DateTime.Now.Month,
                 DateTime.Now.Day,
-                Convert.ToInt32(readOnlySpan[0].ToString(format)),
-                Convert.ToInt32(readOnlySpan[1].ToString(format)),
-                Convert.ToInt32(readOnlySpan[2].ToString(format)),
-                Convert.ToInt32(sb.ToString().TrimStart()));
+                BcdToInt(readOnlySpan[0]),
+                BcdToInt(readOnlySpan[1]),
+                BcdToInt(readOnlySpan[2]), fff);
             }
             catch
             {
@@ -448,20 +531,47 @@ namespace JT808.Protocol.MessagePack
         /// 读取可空类型的五字节日期,HH-mm-ss-msms|HH-mm-ss-fff
         /// </summary>
         /// <param name="format">D2： 10  X2：16</param>
+        [Obsolete("use ReadDateTimeNull_HHmmssfff")]
         public DateTime? ReadDateTimeNull5(string format = "X2")
         {
             DateTime? d;
             try
             {
                 var readOnlySpan = GetReadOnlySpan(5);
-                StringBuilder sb = new StringBuilder(4);
-                sb.Append(readOnlySpan[3].ToString("X2"));
-                sb.Append(readOnlySpan[4].ToString("X2"));
-                int hour = Convert.ToInt32(readOnlySpan[0].ToString(format));
-                int minute = Convert.ToInt32(readOnlySpan[1].ToString(format));
-                int second = Convert.ToInt32(readOnlySpan[2].ToString(format));
-                int millisecond = Convert.ToInt32(sb.ToString().TrimStart());
-                if (hour == 0 && minute == 0 && second == 0 && millisecond == 0) return null;
+                int hour = BcdToInt(readOnlySpan[0]);
+                int minute = BcdToInt(readOnlySpan[1]);
+                int second = BcdToInt(readOnlySpan[2]);
+                var fff = BcdToInt(readOnlySpan[3]) * 100 + BcdToInt(readOnlySpan[4]);
+                if (hour == 0 && minute == 0 && second == 0 && fff == 0) return null;
+                d = new DateTime(
+                DateTime.Now.Year,
+                DateTime.Now.Month,
+                DateTime.Now.Day,
+                hour,
+                minute,
+                second,
+                fff);
+            }
+            catch
+            {
+                return null;
+            }
+            return d;
+        }
+        /// <summary>
+        /// 读取可空类型的五字节日期,HH-mm-ss-msms|HH-mm-ss-fff
+        /// </summary>
+        public DateTime? ReadDateTimeNull_HHmmssfff()
+        {
+            DateTime? d;
+            try
+            {
+                var readOnlySpan = GetReadOnlySpan(5);
+                int hour = BcdToInt(readOnlySpan[0]);
+                int minute = BcdToInt(readOnlySpan[1]);
+                int second = BcdToInt(readOnlySpan[2]);
+                var fff = BcdToInt(readOnlySpan[3]) * 100 + BcdToInt(readOnlySpan[4]);
+                if (hour == 0 && minute == 0 && second == 0 && fff == 0) return null;
                 d = new DateTime(
                 DateTime.Now.Year,
                 DateTime.Now.Month,
@@ -469,7 +579,7 @@ namespace JT808.Protocol.MessagePack
                 hour,
                 minute,
                 second,
-                millisecond);
+                fff);
             }
             catch
             {
@@ -481,19 +591,18 @@ namespace JT808.Protocol.MessagePack
         /// 读取四字节日期，YYYYMMDD
         /// </summary>
         /// <param name="format">D2： 10  X2：16</param>
+        [Obsolete("use ReadDateTime_YYYYMMDD")]
         public DateTime ReadDateTime4(string format = "X2")
         {
             DateTime d;
             try
             {
                 var readOnlySpan = GetReadOnlySpan(4);
-                StringBuilder sb = new StringBuilder(4);
-                sb.Append(readOnlySpan[0].ToString(format));
-                sb.Append(readOnlySpan[1].ToString(format));
+                var year = BcdToInt(readOnlySpan[0]) * 100 + BcdToInt(readOnlySpan[1]);
                 d = new DateTime(
-                Convert.ToInt32(sb.ToString()),
-                Convert.ToInt32(readOnlySpan[2].ToString(format)),
-                Convert.ToInt32(readOnlySpan[3].ToString(format)));
+                    year, 
+                    BcdToInt(readOnlySpan[2]),
+                    BcdToInt(readOnlySpan[3]));
             }
             catch (Exception)
             {
@@ -502,21 +611,61 @@ namespace JT808.Protocol.MessagePack
             return d;   
         }
         /// <summary>
+        /// 读取四字节日期，YYYYMMDD
+        /// </summary>
+        public DateTime ReadDateTime_YYYYMMDD()
+        {
+            DateTime d;
+            try
+            {
+                var readOnlySpan = GetReadOnlySpan(4);
+                var year = BcdToInt(readOnlySpan[0]) * 100 + BcdToInt(readOnlySpan[1]);
+                d = new DateTime(
+                    year,
+                    BcdToInt(readOnlySpan[2]),
+                    BcdToInt(readOnlySpan[3]));
+            }
+            catch (Exception)
+            {
+                d = JT808Constants.UTCBaseTime;
+            }
+            return d;
+        }
+        /// <summary>
         /// 读取可空类型的四字节日期，YYYYMMDD
         /// </summary>
         /// <param name="format">D2： 10  X2：16</param>
+        [Obsolete("use ReadDateTimeNull_YYYYMMDD")]
         public DateTime? ReadDateTimeNull4(string format = "X2")
         {
             DateTime? d;
             try
             {
                 var readOnlySpan = GetReadOnlySpan(4);
-                StringBuilder sb = new StringBuilder(4);
-                sb.Append(readOnlySpan[0].ToString(format));
-                sb.Append(readOnlySpan[1].ToString(format));
-                int year = Convert.ToInt32(sb.ToString());
-                int month = Convert.ToInt32(readOnlySpan[2].ToString(format));
-                int day = Convert.ToInt32(readOnlySpan[3].ToString(format));
+                var year = BcdToInt(readOnlySpan[0]) * 100 + BcdToInt(readOnlySpan[1]);
+                int month = BcdToInt(readOnlySpan[2]);
+                int day = BcdToInt(readOnlySpan[3]);
+                if (year == 0 && month == 0 && day == 0) return null;
+                d = new DateTime(year, month, day);
+            }
+            catch (Exception)
+            {
+                return null;
+            }
+            return d;
+        }
+        /// <summary>
+        /// 读取可空类型的四字节日期，YYYYMMDD
+        /// </summary>
+        public DateTime? ReadDateTimeNull_YYYYMMDD()
+        {
+            DateTime? d;
+            try
+            {
+                var readOnlySpan = GetReadOnlySpan(4);
+                var year = BcdToInt(readOnlySpan[0]) * 100 + BcdToInt(readOnlySpan[1]);
+                int month = BcdToInt(readOnlySpan[2]);
+                int day = BcdToInt(readOnlySpan[3]);
                 if (year == 0 && month == 0 && day == 0) return null;
                 d = new DateTime(year, month, day);
             }
@@ -530,6 +679,7 @@ namespace JT808.Protocol.MessagePack
         /// 读取三字节日期，YYMMDD
         /// </summary>
         /// <param name="format">D2： 10  X2：16</param>
+        [Obsolete("use ReadDateTime_YYMMDD")]
         public DateTime ReadDateTime3(string format = "X2")
         {
             DateTime d;
@@ -537,9 +687,29 @@ namespace JT808.Protocol.MessagePack
             {
                 var readOnlySpan = GetReadOnlySpan(3);
                 d = new DateTime(
-                Convert.ToInt32(readOnlySpan[0].ToString(format)) + JT808Constants.DateLimitYear,
-                Convert.ToInt32(readOnlySpan[1].ToString(format)),
-                Convert.ToInt32(readOnlySpan[2].ToString(format)));
+                BcdToInt(readOnlySpan[0]) + JT808Constants.DateLimitYear,
+                BcdToInt(readOnlySpan[1]),
+                BcdToInt(readOnlySpan[2]));
+            }
+            catch (Exception)
+            {
+                d = JT808Constants.UTCBaseTime;
+            }
+            return d;
+        }
+        /// <summary>
+        /// 读取三字节日期，YYMMDD
+        /// </summary>
+        public DateTime ReadDateTime_YYMMDD()
+        {
+            DateTime d;
+            try
+            {
+                var readOnlySpan = GetReadOnlySpan(3);
+                d = new DateTime(
+                BcdToInt(readOnlySpan[0]) + JT808Constants.DateLimitYear,
+                BcdToInt(readOnlySpan[1]),
+                BcdToInt(readOnlySpan[2]));
             }
             catch (Exception)
             {
@@ -551,15 +721,16 @@ namespace JT808.Protocol.MessagePack
         /// 读取可空类型的三字节日期，YYMMDD
         /// </summary>
         /// <param name="format">D2： 10  X2：16</param>
+        [Obsolete("use ReadDateTimeNull_YYMMDD")]
         public DateTime? ReadDateTimeNull3(string format = "X2")
         {
             DateTime? d;
             try
             {
                 var readOnlySpan = GetReadOnlySpan(3);
-                int year =Convert.ToInt32(readOnlySpan[0].ToString(format));
-                int month=Convert.ToInt32(readOnlySpan[1].ToString(format));
-                int day = Convert.ToInt32(readOnlySpan[2].ToString(format));
+                int year = BcdToInt(readOnlySpan[0]);
+                int month= BcdToInt(readOnlySpan[1]);
+                int day = BcdToInt(readOnlySpan[2]);
                 if (year == 0 && month == 0 && day == 0) return null;
                 d = new DateTime(
                  year + JT808Constants.DateLimitYear, month,day
@@ -572,6 +743,29 @@ namespace JT808.Protocol.MessagePack
             return d;
         }
         /// <summary>
+        /// 读取可空类型的三字节日期，YYMMDD
+        /// </summary>
+        public DateTime? ReadDateTimeNull_YYMMDD()
+        {
+            DateTime? d;
+            try
+            {
+                var readOnlySpan = GetReadOnlySpan(3);
+                int year = BcdToInt(readOnlySpan[0]);
+                int month = BcdToInt(readOnlySpan[1]);
+                int day = BcdToInt(readOnlySpan[2]);
+                if (year == 0 && month == 0 && day == 0) return null;
+                d = new DateTime(
+                 year + JT808Constants.DateLimitYear, month, day
+                );
+            }
+            catch (Exception)
+            {
+                d = JT808Constants.UTCBaseTime;
+            }
+            return d;
+        }
+        /// <summary>
         /// 读取UTC时间类型
         /// </summary>
         /// <returns></returns>

src/JT808.Protocol/MessagePack/JT808MessagePackWriter.cs

@@ -3,6 +3,7 @@ using JT808.Protocol.Enums;
 using System;
 using System.Buffers;
 using System.Buffers.Binary;
+using System.Collections.Generic;
 using System.Text;
 
 namespace JT808.Protocol.MessagePack
@@ -309,27 +310,133 @@ namespace JT808.Protocol.MessagePack
         {
             src.CopyTo(writer.Written.Slice(position));
         }
+
+        /// <summary>
+        /// 整型数据转为BCD BYTE
+        /// 为了兼容int类型，不使用byte做参数
+        /// 支持0xFF一个字节的转换
+        /// </summary>
+        /// <param name="value"></param>
+        /// <returns></returns>
+        public byte IntToBcd(int value)
+        {
+            byte result = 0;
+            if (value <= 0xFF)
+            {
+                //19 00010011
+                //0001 1001
+                int high = value / 10;
+                int low = value % 10;
+                result = (byte)(high << 4 | low); 
+            }
+            return result;
+        }
+
+        /// <summary>
+        /// 整型数据转为BCD BYTE[]
+        /// </summary>
+        /// <param name="value">整数值</param>
+        /// <param name="list">bytes</param>
+        /// <param name="count">字节数>=整数值</param>
+        public void IntToBcd(int value, Span<byte> list, int count)
+        {
+            int level = count - 1;
+            var high = value / 100;
+            var low = value % 100;
+            if (high > 0)
+            {
+                IntToBcd(high, list, --count);
+            }
+            byte res = (byte)(((low / 10) << 4) + (low % 10));
+            list[level] = res;
+        }
+
+        /// <summary>
+        /// 整型数据转为BCD BYTE[]
+        /// </summary>
+        /// <param name="value">整数值</param>
+        /// <param name="list">bytes</param>
+        /// <param name="byteCount">字节数>=整数值</param>
+        public void IntToBcd(long value, Span<byte> list, int byteCount)
+        {
+            int level = byteCount - 1;
+            if (level < 0) return;
+            var high = value / 100;
+            var low = value % 100;
+            if (high > 0)
+            {
+                IntToBcd(high, list, --byteCount);
+            }
+            byte res = (byte)(((low / 10) << 4) + (low % 10));
+            list[level] = res;
+        }
+
+        /// <summary>
+        /// 写入BCD编码数据
+        /// </summary>
+        /// <param name="value">整数值</param>
+        /// <param name="byteCount">字节数>=整数值</param>
+        public void WriteBCD(in long value, in int byteCount)
+        {
+            var span = writer.Free;
+            IntToBcd(value, writer.Free, byteCount);
+            writer.Advance(byteCount);
+        }
+
+        /// <summary>
+        /// 写入BCD编码数据
+        /// </summary>
+        /// <param name="value">整数值</param>
+        /// <param name="count">字节数>=整数值</param>
+        public void WriteBCD(in int value, in int count)
+        {
+            var span = writer.Free;
+            IntToBcd(value, writer.Free, count);
+            writer.Advance(count);
+        }
+
         /// <summary>
         /// 写入六个字节的日期类型,yyMMddHHmmss
         /// </summary>
         /// <param name="value"></param>
         /// <param name="fromBase"></param>
+        [Obsolete("use WriteDateTime_yyMMddHHmmss")]
         public void WriteDateTime6(in DateTime value, in int fromBase = 16)
         {
             var span = writer.Free;
-            span[0] = Convert.ToByte(value.ToString("yy"), fromBase);
-            span[1] = Convert.ToByte(value.ToString("MM"), fromBase);
-            span[2] = Convert.ToByte(value.ToString("dd"), fromBase);
-            span[3] = Convert.ToByte(value.ToString("HH"), fromBase);
-            span[4] = Convert.ToByte(value.ToString("mm"), fromBase);
-            span[5] = Convert.ToByte(value.ToString("ss"), fromBase);
+            int yy = value.Year - JT808Constants.DateLimitYear;
+            span[0] = IntToBcd(yy);
+            span[1] = IntToBcd(value.Month);
+            span[2] = IntToBcd(value.Day);
+            span[3] = IntToBcd(value.Hour);
+            span[4] = IntToBcd(value.Minute);
+            span[5] = IntToBcd(value.Second);
             writer.Advance(6);
         }
+
+        /// <summary>
+        /// 写入六个字节的日期类型,yyMMddHHmmss
+        /// </summary>
+        /// <param name="value"></param>
+        public void WriteDateTime_yyMMddHHmmss(in DateTime value)
+        {
+            var span = writer.Free;
+            int yy = value.Year - JT808Constants.DateLimitYear;
+            span[0] = IntToBcd(yy);
+            span[1] = IntToBcd(value.Month);
+            span[2] = IntToBcd(value.Day);
+            span[3] = IntToBcd(value.Hour);
+            span[4] = IntToBcd(value.Minute);
+            span[5] = IntToBcd(value.Second);
+            writer.Advance(6);
+        }
+
         /// <summary>
         /// 写入六个字节的可空日期类型,yyMMddHHmmss
         /// </summary>
         /// <param name="value"></param>
         /// <param name="fromBase"></param>
+        [Obsolete("use WriteDateTime_yyMMddHHmmss")]
         public void WriteDateTime6(in DateTime? value, in int fromBase = 16)
         {
             var span = writer.Free;
@@ -344,58 +451,136 @@ namespace JT808.Protocol.MessagePack
             }
             else
             {
-                span[0] = Convert.ToByte(value.Value.ToString("yy"), fromBase);
-                span[1] = Convert.ToByte(value.Value.ToString("MM"), fromBase);
-                span[2] = Convert.ToByte(value.Value.ToString("dd"), fromBase);
-                span[3] = Convert.ToByte(value.Value.ToString("HH"), fromBase);
-                span[4] = Convert.ToByte(value.Value.ToString("mm"), fromBase);
-                span[5] = Convert.ToByte(value.Value.ToString("ss"), fromBase);
+                int yy = value.Value.Year - JT808Constants.DateLimitYear;
+                span[0] = IntToBcd(yy);
+                span[1] = IntToBcd(value.Value.Month);
+                span[2] = IntToBcd(value.Value.Day);
+                span[3] = IntToBcd(value.Value.Hour);
+                span[4] = IntToBcd(value.Value.Minute);
+                span[5] = IntToBcd(value.Value.Second);
+            }
+            writer.Advance(6);
+        }
+
+        /// <summary>
+        /// 写入六个字节的可空日期类型,yyMMddHHmmss
+        /// </summary>
+        /// <param name="value"></param>
+        public void WriteDateTime_yyMMddHHmmss(in DateTime? value)
+        {
+            var span = writer.Free;
+            if (value == null || value.HasValue)
+            {
+                span[0] = 0;
+                span[1] = 0;
+                span[2] = 0;
+                span[3] = 0;
+                span[4] = 0;
+                span[5] = 0;
+            }
+            else
+            {
+                int yy = value.Value.Year - JT808Constants.DateLimitYear;
+                span[0] = IntToBcd(yy);
+                span[1] = IntToBcd(value.Value.Month);
+                span[2] = IntToBcd(value.Value.Day);
+                span[3] = IntToBcd(value.Value.Hour);
+                span[4] = IntToBcd(value.Value.Minute);
+                span[5] = IntToBcd(value.Value.Second);
             }
             writer.Advance(6);
         }
+
         /// <summary>
         /// 写入五个字节的日期类型,HH-mm-ss-msms或HH-mm-ss-fff
         /// </summary>
         /// <param name="value"></param>
         /// <param name="fromBase"></param>
+        [Obsolete("use WriteDateTime_HHmmssfff")]
         public void WriteDateTime5(in DateTime value, in int fromBase = 16)
         {
             var span = writer.Free;
-            span[0] = Convert.ToByte(value.ToString("HH"), fromBase);
-            span[1] = Convert.ToByte(value.ToString("mm"), fromBase);
-            span[2] = Convert.ToByte(value.ToString("ss"), fromBase);
-            var msSpan = value.Millisecond.ToString().PadLeft(4,'0').AsSpan();
-            span[3] = Convert.ToByte(msSpan.Slice(0, 2).ToString(), fromBase);
-            span[4] = Convert.ToByte(msSpan.Slice(2, 2).ToString(), fromBase);
-            writer.Advance(5);
+            span[0] = IntToBcd(value.Hour);
+            span[1] = IntToBcd(value.Minute);
+            span[2] = IntToBcd(value.Second);
+            writer.Advance(3);
+            IntToBcd(value.Millisecond, writer.Free, 2);
+            writer.Advance(2);
+        }
+
+        /// <summary>
+        /// 写入五个字节的日期类型,HH-mm-ss-msms或HH-mm-ss-fff
+        /// </summary>
+        /// <param name="value"></param>
+        public void WriteDateTime_HHmmssfff(in DateTime value)
+        {
+            var span = writer.Free;
+            span[0] = IntToBcd(value.Hour);
+            span[1] = IntToBcd(value.Minute);
+            span[2] = IntToBcd(value.Second);
+            writer.Advance(3);
+            IntToBcd(value.Millisecond, writer.Free, 2);
+            writer.Advance(2);
         }
+
         /// <summary>
         /// 写入五个字节的可空日期类型,HH-mm-ss-msms或HH-mm-ss-fff
         /// </summary>
         /// <param name="value"></param>
         /// <param name="fromBase"></param>
+        [Obsolete("use WriteDateTime_HHmmssfff")]
         public void WriteDateTime5(in DateTime? value, in int fromBase = 16)
         {
-            var span = writer.Free;
             if (value == null || value.HasValue)
             {
+                var span = writer.Free;
                 span[0] = 0;
                 span[1] = 0;
                 span[2] = 0;
                 span[3] = 0;
                 span[4] = 0;
+                writer.Advance(5);
             }
             else
             {
-                span[0] = Convert.ToByte(value.Value.ToString("HH"), fromBase);
-                span[1] = Convert.ToByte(value.Value.ToString("mm"), fromBase);
-                span[2] = Convert.ToByte(value.Value.ToString("ss"), fromBase);
-                var msSpan = value.Value.Millisecond.ToString().PadLeft(4, '0').AsSpan();
-                span[3] = Convert.ToByte(msSpan.Slice(0, 2).ToString(), fromBase);
-                span[4] = Convert.ToByte(msSpan.Slice(2, 2).ToString(), fromBase);
+                var span = writer.Free;
+                span[0] = IntToBcd(value.Value.Hour);
+                span[1] = IntToBcd(value.Value.Minute);
+                span[2] = IntToBcd(value.Value.Second);
+                writer.Advance(3);
+                IntToBcd(value.Value.Millisecond, writer.Free, 2);
+                writer.Advance(2);
             }
-            writer.Advance(5);
         }
+
+        /// <summary>
+        /// 写入五个字节的可空日期类型,HH-mm-ss-msms或HH-mm-ss-fff
+        /// </summary>
+        /// <param name="value"></param>
+        public void WriteDateTime_HHmmssfff(in DateTime? value)
+        {
+            if (value == null || value.HasValue)
+            {
+                var span = writer.Free;
+                span[0] = 0;
+                span[1] = 0;
+                span[2] = 0;
+                span[3] = 0;
+                span[4] = 0;
+                writer.Advance(5);
+            }
+            else
+            {
+                var span = writer.Free;
+                span[0] = IntToBcd(value.Value.Hour);
+                span[1] = IntToBcd(value.Value.Minute);
+                span[2] = IntToBcd(value.Value.Second);
+                writer.Advance(3);
+                IntToBcd(value.Value.Millisecond, writer.Free, 2);
+                writer.Advance(2);
+            }
+        }
+
         /// <summary>
         /// 写入UTC日期类型
         /// </summary>
@@ -412,20 +597,35 @@ namespace JT808.Protocol.MessagePack
             }
             writer.Advance(8);
         }
+
         /// <summary>
         /// 写入四个字节的日期类型,YYYYMMDD BCD[4] 数据形如：20200101
         /// </summary>
         /// <param name="value"></param>
         /// <param name="fromBase"></param>
+        [Obsolete("use WriteDateTime_YYYYMMDD")]
         public void WriteDateTime4(in DateTime value, in int fromBase = 16)
         {
+            IntToBcd(value.Year, writer.Free, 2);
+            writer.Advance(2);
             var span = writer.Free;
-            var yearSpan=value.ToString("yyyy").AsSpan();
-            span[0] = Convert.ToByte(yearSpan.Slice(0, 2).ToString(), fromBase);
-            span[1] = Convert.ToByte(yearSpan.Slice(2, 2).ToString(), fromBase);
-            span[2] = Convert.ToByte(value.ToString("MM"), fromBase);
-            span[3] = Convert.ToByte(value.ToString("dd"), fromBase);
-            writer.Advance(4);
+            span[0] = IntToBcd(value.Month);
+            span[1] = IntToBcd(value.Day);
+            writer.Advance(2);
+        }
+
+        /// <summary>
+        /// 写入四个字节的日期类型,YYYYMMDD BCD[4] 数据形如：20200101
+        /// </summary>
+        /// <param name="value"></param>
+        public void WriteDateTime_YYYYMMDD(in DateTime value)
+        {
+            IntToBcd(value.Year, writer.Free, 2);
+            writer.Advance(2);
+            var span = writer.Free;
+            span[0] = IntToBcd(value.Month);
+            span[1] = IntToBcd(value.Day);
+            writer.Advance(2);
         }
 
         /// <summary>
@@ -433,25 +633,53 @@ namespace JT808.Protocol.MessagePack
         /// </summary>
         /// <param name="value"></param>
         /// <param name="fromBase"></param>
+        [Obsolete("use WriteDateTime_YYYYMMDD")]
         public void WriteDateTime4(in DateTime? value, in int fromBase = 16)
         {
-            var span = writer.Free;
             if (value==null || value.HasValue)
             {
+                var span = writer.Free;
                 span[0] = 0;
                 span[1] = 0;
                 span[2] = 0;
                 span[3] = 0;
+                writer.Advance(4);
             }
             else
             {
-                var yearSpan = value.Value.ToString("yyyy").AsSpan();
-                span[0] = Convert.ToByte(yearSpan.Slice(0, 2).ToString(), fromBase);
-                span[1] = Convert.ToByte(yearSpan.Slice(2, 2).ToString(), fromBase);
-                span[2] = Convert.ToByte(value.Value.ToString("MM"), fromBase);
-                span[3] = Convert.ToByte(value.Value.ToString("dd"), fromBase);
+                IntToBcd(value.Value.Year, writer.Free, 2);
+                writer.Advance(2);
+                var span = writer.Free;
+                span[0] = IntToBcd(value.Value.Month);
+                span[1] = IntToBcd(value.Value.Day);
+                writer.Advance(2);
+            }    
+        }
+
+        /// <summary>
+        /// 写入四个字节的可空日期类型,YYYYMMDD BCD[4]数据形如:20200101
+        /// </summary>
+        /// <param name="value"></param>
+        public void WriteDateTime_YYYYMMDD(in DateTime? value)
+        {
+            if (value == null || value.HasValue)
+            {
+                var span = writer.Free;
+                span[0] = 0;
+                span[1] = 0;
+                span[2] = 0;
+                span[3] = 0;
+                writer.Advance(4);
+            }
+            else
+            {
+                IntToBcd(value.Value.Year, writer.Free, 2);
+                writer.Advance(2);
+                var span = writer.Free;
+                span[0] = IntToBcd(value.Value.Month);
+                span[1] = IntToBcd(value.Value.Day);
+                writer.Advance(2);
             }
-            writer.Advance(4);
         }
 
         /// <summary>
@@ -459,20 +687,35 @@ namespace JT808.Protocol.MessagePack
         /// </summary>
         /// <param name="value"></param>
         /// <param name="fromBase"></param>
+        [Obsolete("use WriteDateTime_YYMMDD")]
         public void WriteDateTime3(in DateTime value, in int fromBase = 16)
         {
             var span = writer.Free;
-            span[0] = Convert.ToByte(value.ToString("yy"), fromBase);
-            span[1] = Convert.ToByte(value.ToString("MM"), fromBase);
-            span[2] = Convert.ToByte(value.ToString("dd"), fromBase);
+            int yy = value.Year - JT808Constants.DateLimitYear;
+            span[0] = IntToBcd(yy);
+            span[1] = IntToBcd(value.Month);
+            span[2] = IntToBcd(value.Day);
+            writer.Advance(3);
+        }
+        /// <summary>
+        /// 写入三个字节的日期类型,YYMMDD 数据形如：20200101
+        /// </summary>
+        /// <param name="value"></param>
+        public void WriteDateTime_YYMMDD(in DateTime value)
+        {
+            var span = writer.Free;
+            int yy = value.Year - JT808Constants.DateLimitYear;
+            span[0] = IntToBcd(yy);
+            span[1] = IntToBcd(value.Month);
+            span[2] = IntToBcd(value.Day);
             writer.Advance(3);
         }
-
         /// <summary>
         /// 写入三个字节的可空日期类型,YYMMDD 数据形如：20200101
         /// </summary>
         /// <param name="value"></param>
         /// <param name="fromBase"></param>
+        [Obsolete("use WriteDateTime_YYMMDD")]
         public void WriteDateTime3(in DateTime? value, in int fromBase = 16)
         {
             var span = writer.Free;
@@ -484,9 +727,32 @@ namespace JT808.Protocol.MessagePack
             }
             else
             {
-                span[0] = Convert.ToByte(value.Value.ToString("yy"), fromBase);
-                span[1] = Convert.ToByte(value.Value.ToString("MM"), fromBase);
-                span[2] = Convert.ToByte(value.Value.ToString("dd"), fromBase);
+                int yy = value.Value.Year - JT808Constants.DateLimitYear;
+                span[0] = IntToBcd(yy);
+                span[1] = IntToBcd(value.Value.Month);
+                span[2] = IntToBcd(value.Value.Day);
+            }
+            writer.Advance(3);
+        }
+        /// <summary>
+        /// 写入三个字节的可空日期类型,YYMMDD 数据形如：20200101
+        /// </summary>
+        /// <param name="value"></param>
+        public void WriteDateTime_YYMMDD(in DateTime? value)
+        {
+            var span = writer.Free;
+            if (value == null || value.HasValue)
+            {
+                span[0] = 0;
+                span[1] = 0;
+                span[2] = 0;
+            }
+            else
+            {
+                int yy = value.Value.Year - JT808Constants.DateLimitYear;
+                span[0] = IntToBcd(yy);
+                span[1] = IntToBcd(value.Value.Month);
+                span[2] = IntToBcd(value.Value.Day);
             }
             writer.Advance(3);
         }