*    *   *  *   *  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) Disable Mail Alert by Cron: 0 1 5 10 * /path/to/script.sh >/dev/null 2>&1 or 0 1 5 10 * /path/to/script.sh &> /dev/null or you can also set MAILTO variable at the top of file : MAILTO=""

Examples:

crontab every 15 minute:
*/15 * * * * /path/to/command

Every sunday 5.00 pm:
00 17 * * 0 /path/to/command