Crontab

# Will run "YourCommand" at 00:00 every day of every months
#Min   Hours   D of the M       Month   D of the Week   Command
0      0       *                *       *               YourCommand

# Will run "YourCommand" at 13:30 every day of every months
30     13      *                *       *               YourCommand
Or, as a single line, you can run a command every x hours, like so:

# Will run "YourCommand" every 12 hours
0   */12   *   *   *   YourCommand
or

# Will run "YourCommand" at 1am and 1pm every day
0   1,13   *   *   *   YourCommand arg1 arg2

reference stackoverflow