Epoch Time Conversion

JSON Web Token (JWT) tokens use so-called Epoch or Unix time to represent date/times, which is the number of seconds that have elapsed since January 1, 1970 (midnight UTC/GMT).

DateTimeOffset To Epoch Time

In .NET, you can convert DateTimeOffset to Unix time via the two methods of ToUnixTimeSeconds and ToUnixTimeMilliseconds:

var seconds = DateTimeOffset.UtcNow.ToUnixTimeSeconds();
var milliseconds = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds();

DateTime To Epoch Time obsolete

IdentityModel contains extensions methods for DateTime to convert to/from Unix time:

var dt = DateTime.UtcNow;
// The time returned is in seconds
var unix = dt.ToEpochTime();