Yet another C# datetime extensions to convert DateTime to Unix timestamps.

DateTimeExtensions.cs

using System;

namespace MyExtensions
{
    public static class DateTimeExtensions
    {
        public const long EpochTicks = 621355968000000000;
        public const long TicksPeriod = 10000000;
        public const long TicksPeriodMs = 10000;

        //epoch time
        public static readonly DateTime Epoch = new DateTime(EpochTicks, DateTimeKind.Utc);

        /// <summary>
        /// Number of milliseconds since epoch(1/1/1970).
        /// </summary>
        /// <param name="date">DateTime to convert</param>
        /// <returns>Number of milliseconds since 1/1/1970 (Unix timestamp)</returns>
        public static long ToMilliSecondsTimestamp(this DateTime date)
        {
            long ts = (date.Ticks - EpochTicks) / TicksPeriodMs;
            return ts;
        }

        /// <summary>
        /// Number of seconds since epoch(1/1/1970).
        /// </summary>
        /// <param name="date">DateTime to convert</param>
        /// <returns>Number of seconds since 1/1/1970 (Unix timestamp)</returns>
        public static long ToSecondsTimestamp(this DateTime date)
        {
            long ts = (date.Ticks - EpochTicks) / TicksPeriod;
            return ts;
        }

        /// <summary>
        /// Round a timestamp in seconds.
        /// </summary>
        /// <param name="date">DateTime to convert</param>
        /// <param name="factor">Round factor in seconds.</param>
        /// <returns>Rounded Timestamp in seconds.</returns>
        public static long ToRoundedSecondsTimestamp(this DateTime date, long factor)
        {
            return ((long)date.ToSecondsTimestamp() / factor) * factor;
        }
    }
}