using System;

​

long BaseDateTicks = new DateTime(1900, 1, 1).Ticks;

​

Guid NewGuid()

{

    var guidArray = Guid.NewGuid().ToByteArray();

    var now = DateTime.UtcNow;

    // Get the days and milliseconds which will be used to build the byte string 

    var days = new TimeSpan(now.Ticks - BaseDateTicks);

    var msecs = now.TimeOfDay;

    // Convert to a byte array 

    // Note that SQL Server is accurate to 1/300th of a millisecond so we divide by 3.333333 

    var daysArray = BitConverter.GetBytes(days.Days);

    var msecsArray = BitConverter.GetBytes((long)(msecs.TotalMilliseconds / 3.333333));

    // Reverse the bytes to match SQL Servers ordering 

    Array.Reverse(daysArray);

    Array.Reverse(msecsArray);

    // Copy the bytes into the guid 

    Array.Copy(daysArray, daysArray.Length - 2, guidArray, guidArray.Length - 6, 2);

    Array.Copy(msecsArray, msecsArray.Length - 4, guidArray, guidArray.Length - 4, 4);

    return new Guid(guidArray);

}

​

DateTime ExtractDateTime(Guid guid)

{

    var guidArray = guid.ToByteArray();

    var daysArray = new byte[4];

    var msecsArray = new byte[8];

    // Copy the bytes out of the guid 

    Array.Copy(guidArray, guidArray.Length - 6, daysArray, daysArray.Length - 2, 2);

    Array.Copy(guidArray, guidArray.Length - 4, msecsArray, msecsArray.Length - 4, 4);

    // Reverse the bytes to match SQL Servers ordering 

    Array.Reverse(daysArray);

    Array.Reverse(msecsArray);

    // Convert from a byte array 

    // Note that SQL Server is accurate to 1/300th of a millisecond so we multiply by 3.333333 

    var days = new TimeSpan(BitConverter.ToInt32(daysArray, 0), 0, 0, 0);

    var totalMilliseconds = new TimeSpan(0, 0, 0, 0, (int)(BitConverter.ToInt64(msecsArray, 0) * 3.333333));

    return new DateTime(days.Ticks + BaseDateTicks) + totalMilliseconds;

}

​

var newGuid = NewGuid();

Console.WriteLine(newGuid);

​

var origDateTime = ExtractDateTime(newGuid);

Console.WriteLine(origDateTime);