will it trigger at the start of a week or end of it ?
Oh woah, this question has been here for a really long time, sorry about that @atian25, hopefully the answer would help others in the future too 
Crons trigger at the same time you put them in, on a daily, weekly or monthly basis.
Say for example I put in my cron job at 15:00 CEST on a Tuesday, the daily job would trigger same time Wednesday, the weekly one same time the following Tuesday and so on.