It actually goes against the rules to set a deadline by which all tips must be in. The rules state that:
"you have to send your picks, before the first match of the day starts, if you send your picks late, then all the picks for the matches already started or finished won't be counted"
I'd suggest that you'll just have to find out which matches started when
If you check out the "OOP and Scores"-thread you'd probably be able to set the approximate times for the matches. Just find out when the first score-update for each match was posted, and you've got your starting time.