.net datetime get unix timestamp code example

Example 1: c# convert datetime to unix timestamp

Int32 unixTimestamp = (Int32)(DateTime.UtcNow.Subtract(new DateTime(1970, 1, 1))).TotalSeconds;

Example 2: epoch

Epoch timestamp is a unit of measurement for time. It is the number of
seconds elapsed since the countdown has started. 

Beginning epochs per system:
macOS - January 1, 1904
Windows - January 1, 1601
Unix - January 1, 1970