Possible Duplicate:
How to convert UNIX timestamp to DateTime and vice versa?
How can I create a unix timestamp in C#? (e.g. 2012-10-10 14:00:00 -> 1349877600)
private double ConvertToTimestamp(DateTime value)
{
//create Timespan by subtracting the value provided from
//the Unix Epoch
TimeSpan span = (value - new DateTime(1970, 1, 1, 0, 0, 0, 0).ToLocalTime());
//return the total seconds (which is a UNIX timestamp)
return (double)span.TotalSeconds;
}