To see the list of cronjobs and when they are scheduled run the command "crontab -l". The fields are:
Min, Hour, Day of Month, Month, Day of Week, Command. Most of the fields are combined with AND, however the Day of Month and Day of Week fields are combined with OR. So if you have something like:
00 0 1-7 * 5 echo "First Friday of the Month"
It WILL NOT just echo on the first Friday of the month, it will echo EVERY Friday and everyday of the month from the first through the seventh.
It is basically saying:
if ((MIN == 00) && (HOUR == 0) && (MONTH is any) && ((DOM < 7) || (DOW == 5))) run the command.
As far as when certain things are run on YOUR system, I'd have to see the output of "crontab -l" to know.