os.time()

By default, os.time() returns the current time as a Unix Epoch Time. A table argument can also be used to return a time as a Unix Epoch integer representing the date and time specified by the given table.

Open

If specified, the table must include fields for year, month, and day. Optionally, you can include fields for hour, min, sec, and isdst (boolean true for Daylight Savings Time).

os.time() can be used as an argument for calling os.date() and os.difftime().