Decode any cron expression into plain language and see when it will fire next. Clickable examples and a syntax cheatsheet help you build your own schedule.
Minute, hour, day of month, month, day of week — in that order. * means "every", */5 means "every 5".
0 3 * * * — minute 0, hour 3, any day, month and weekday.
Setting both day-of-month and day-of-week makes cron fire when either matches — leave one as *.