i use this simple table to determine how im going to put the hours days month years or weeks on my crontabs



at that interval.
* * * * * command to be executed
- - - - -
| | | | |
| | | | +----- day of week (0 - 6) (Sunday=0)
| | | +------- month (1 - 12)
| | +--------- day of month (1 - 31)
| +----------- hour (0 - 23)
+------------- min (0 - 59)

Special stringMeaning
@rebootRun once, at startup.
@yearlyRun once a year, “0 0 1 1 *”.
@annually(same as @yearly)
@monthlyRun once a month, “0 0 1 * *”.
@weeklyRun once a week, “0 0 * * 0″.
@dailyRun once a day, “0 0 * * *”.
@midnight(same as @daily)
@hourly Run once an hour, “0 * * * *”.
if you need more help, this link will give you more info:

Crontab Format: Minute Hour Day Week Month