Seconds or milliseconds?
Unix time in most back-end systems is in seconds; JavaScript's Date.now() returns milliseconds. A 13-digit value is almost always milliseconds. The converter detects this automatically.
Cron and time zones
Cron runs in the scheduler's time zone. A job set to 0 9 * * * on a UTC server runs at 09:00 UTC, which may be a different local hour for your users.
