Return the number of milliseconds since the Unix epoch (1 Jan., 1970 UTC) for a given DateTime value.

   
 


//http://www.bouncycastle.org/
//MIT X11 License

using System;

namespace Org.BouncyCastle.Utilities.Date
{
  public class DateTimeUtilities
  {
    public static readonly DateTime UnixEpoch = new DateTime(1970, 1, 1);

    private DateTimeUtilities()
    {
    }

    /// <summary>
    /// Return the number of milliseconds since the Unix epoch (1 Jan., 1970 UTC) for a given DateTime value.
    /// </summary>
    /// <param name="dateTime">A UTC DateTime value not before epoch.</param>
    /// <returns>Number of whole milliseconds after epoch.</returns>
    /// <exception cref="ArgumentException">&#039;dateTime&#039; is before epoch.</exception>
    public static long DateTimeToUnixMs(DateTime dateTime)
    {
      if (dateTime.CompareTo(UnixEpoch) < 0)
        throw new ArgumentException("DateTime value may not be before the epoch", "dateTime");

      return (dateTime.Ticks - UnixEpoch.Ticks) / TimeSpan.TicksPerMillisecond;
    }

    /// <summary>
    /// Create a DateTime value from the number of milliseconds since the Unix epoch (1 Jan., 1970 UTC).
    /// </summary>
    /// <param name="unixMs">Number of milliseconds since the epoch.</param>
    /// <returns>A UTC DateTime value</returns>
    public static DateTime UnixMsToDateTime(long unixMs)
    {
      return new DateTime(unixMs * TimeSpan.TicksPerMillisecond + UnixEpoch.Ticks);
    }

    /// <summary>
    /// Return the current number of milliseconds since the Unix epoch (1 Jan., 1970 UTC).
    /// </summary>
    public static long CurrentUnixMs()
    {
      return DateTimeToUnixMs(DateTime.UtcNow);
    }
  }
}