Php – convert any date string to timestamp without timezone

Note to readers: Several commenters have pointed out some problems in this answer (related particularly to the first suggestion). Refer to the comments section for more information.

DateTime.UtcNow.ToString("yyyy-MM-ddTHH\\:mm\\:ss.fffffffzzz");

Using custom date-time formatting, this gives you a date similar to
2008-09-22T13:57:31.2311892-04:00.

Another way is:

DateTime.UtcNow.ToString("o");

which uses the standard "round-trip" style (ISO 8601) to give you
2008-09-22T14:01:54.9571247Z.

To get the specified format, you can use:

DateTime.UtcNow.ToString("yyyy-MM-ddTHH:mm:ssZ")

Here's what you need:

public static DateTime UnixTimeStampToDateTime( double unixTimeStamp )
{
    // Unix timestamp is seconds past epoch
    DateTime dateTime = new DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc);
    dateTime = dateTime.AddSeconds( unixTimeStamp ).ToLocalTime();
    return dateTime;
}

Or, for Java (which is different because the timestamp is in milliseconds, not seconds):

public static DateTime JavaTimeStampToDateTime( double javaTimeStamp )
{
    // Java timestamp is milliseconds past epoch
    DateTime dateTime = new DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc);
    dateTime = dateTime.AddMilliseconds( javaTimeStamp ).ToLocalTime();
    return dateTime;
}