Returns the time in seconds since 19700101T000000Z.
The optional arguments are in order:
Year (1900..).
Month of year (1..12).
Day of month (1..31).
Hour of day (0..23).
Minute of hour (0..59).
Seconds of minute (0..60).
Timezone offset from UTC in seconds. Defaults to the local timezone.
If no arguments are given, the current time is returned.
