Time & Date

Time is where correct-looking code goes wrong quietly. A Unix timestamp has no time zone, a calendar date has no instant, and the gap between the two is responsible for a large share of off-by-one-day bugs.

The timestamp converter reads seconds and milliseconds and tells you which it assumed, because a ten-digit and a thirteen-digit number mean the same moment scaled by a thousand. The time zone converter exists for the question a calendar invite cannot answer: what a fixed instant looks like to someone else, including on the days a DST change makes the arithmetic non-obvious.

The cron pair goes both ways. The parser turns an expression into the next run times in plain language, which is how you catch a schedule that fires every minute instead of every hour. The generator builds the expression from the schedule you describe. Note that @reboot and other shorthands are handled by the cron daemon rather than the five-field syntax.