In general, the date and time of football matches is confirmed between 10 and 20 days prior to the event. Confirmation of dates depends on the Football Federation in each country, in some cases the final date is announced and confirmed 1 month earlier. It is the responsibility of each client to keep up to date of any changes and confirm the date and time in the days prior to the match.
When you buy your tickets, the session is confirmed (the match, who will play), but not the date. You can check the official website of the League that you are going to watch.