using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        string uuidString = "9e5713bb-bb4c-11e8-9d6c-1866da6cbe53";

        Guid gui = new Guid(uuidString);

        DateTime dateTimeFromGuid = GuidGenerator.GetDateTime(gui);

        Console.WriteLine(dateTimeFromGuid.ToString("dd/MM/yyyy hh:mm:ss"));

        Guid guidFromDateTime = GuidGenerator.GenerateTimeBasedGuid(dateTimeFromGuid);

        Console.WriteLine(guidFromDateTime); //7909dbbb-bb33-11e8-9f6a-95d8e90ccf10 

    }

}

​

public static partial class GuidGenerator

    {

        // number of bytes in guid

        public const int ByteArraySize = 16;

​

        // multiplex variant info

        public const int VariantByte = 8;

        public const int VariantByteMask = 0x3f;

        public const int VariantByteShift = 0x80;

​

        // multiplex version info

        public const int VersionByte = 7;

        public const int VersionByteMask = 0x0f;

        public const int VersionByteShift = 4;

​

        // indexes within the uuid array for certain boundaries

        private const byte TimestampByte = 0;

        private const byte GuidClockSequenceByte = 8;

        private const byte NodeByte = 10;

​

        // offset to move from 1/1/0001, which is 0-time for .NET, to gregorian 0-time of 10/15/1582

        private static readonly DateTimeOffset GregorianCalendarStart = new DateTimeOffset(1582, 10, 15, 0, 0, 0, TimeSpan.Zero);

​

        // random clock sequence and node

        public static byte[] DefaultClockSequence { get; set; }

        public static byte[] DefaultNode { get; set; }

​

        static GuidGenerator()

        {

            DefaultClockSequence = new byte[2];

            DefaultNode = new byte[6];

​

            var random = new Random();

            random.NextBytes(DefaultClockSequence);

            random.NextBytes(DefaultNode);

        }

​

        public static GuidVersion GetVersion(this Guid guid)

        {

            byte[] bytes = guid.ToByteArray();

            return (GuidVersion)((bytes[VersionByte] & 0xFF) >> VersionByteShift);

        }

​

        public static DateTimeOffset GetDateTimeOffset(Guid guid)

        {

            byte[] bytes = guid.ToByteArray();

​

            // reverse the version

            bytes[VersionByte] &= (byte)VersionByteMask;

            bytes[VersionByte] |= (byte)((byte)GuidVersion.TimeBased >> VersionByteShift);

​

            byte[] timestampBytes = new byte[8];

            Array.Copy(bytes, TimestampByte, timestampBytes, 0, 8);

​

            long timestamp = BitConverter.ToInt64(timestampBytes, 0);

            long ticks = timestamp + GregorianCalendarStart.Ticks;

​

            return new DateTimeOffset(ticks, TimeSpan.Zero);

        }

​

        public static DateTime GetDateTime(Guid guid)

        {

            return GetDateTimeOffset(guid).DateTime;

        }

​

        public static DateTime GetLocalDateTime(Guid guid)

        {

            return GetDateTimeOffset(guid).LocalDateTime;

        }

​

        public static DateTime GetUtcDateTime(Guid guid)

        {

            return GetDateTimeOffset(guid).UtcDateTime;

        }

​

        public static Guid GenerateTimeBasedGuid()

        {

            return GenerateTimeBasedGuid(DateTimeOffset.UtcNow, DefaultClockSequence, DefaultNode);

        }

​

        public static Guid GenerateTimeBasedGuid(DateTime dateTime)

        {

            return GenerateTimeBasedGuid(dateTime, DefaultClockSequence, DefaultNode);

        }

​

        public static Guid GenerateTimeBasedGuid(DateTimeOffset dateTime)

        {

            return GenerateTimeBasedGuid(dateTime, DefaultClockSequence, DefaultNode);

        }

​

        public static Guid GenerateTimeBasedGuid(DateTime dateTime, byte[] clockSequence, byte[] node)

        {

            return GenerateTimeBasedGuid(new DateTimeOffset(dateTime), clockSequence, node);

        }

​

        public static Guid GenerateTimeBasedGuid(DateTimeOffset dateTime, byte[] clockSequence, byte[] node)

        {

            if (clockSequence == null)

                throw new ArgumentNullException("clockSequence");

​

            if (node == null)

                throw new ArgumentNullException("node");

​

            if (clockSequence.Length != 2)

                throw new ArgumentOutOfRangeException("clockSequence", "The clockSequence must be 2 bytes.");

​

            if (node.Length != 6)

                throw new ArgumentOutOfRangeException("node", "The node must be 6 bytes.");

​

            long ticks = (dateTime - GregorianCalendarStart).Ticks;

            byte[] guid = new byte[ByteArraySize];

            byte[] timestamp = BitConverter.GetBytes(ticks);

​

            // copy node

            Array.Copy(node, 0, guid, NodeByte, Math.Min(6, node.Length));

​

            // copy clock sequence

            Array.Copy(clockSequence, 0, guid, GuidClockSequenceByte, Math.Min(2, clockSequence.Length));

​

            // copy timestamp

            Array.Copy(timestamp, 0, guid, TimestampByte, Math.Min(8, timestamp.Length));

​

            // set the variant

            guid[VariantByte] &= (byte)VariantByteMask;

            guid[VariantByte] |= (byte)VariantByteShift;

​

            // set the version

            guid[VersionByte] &= (byte)VersionByteMask;

            guid[VersionByte] |= (byte)((byte)GuidVersion.TimeBased << VersionByteShift);

​

            return new Guid(guid);

        }

    }

​

public enum GuidVersion

    {

        TimeBased = 0x01,

        Reserved = 0x02,

        NameBased = 0x03,

        Random = 0x04

    }