For all major badminton tournaments, not just the Olympics, they only use a limited number of courts for major games (e.g semifinals and finals). As a result the scheduling works in a way for example on one day, on a specific court:
- Women's Doubles Semi Final #1 4pm
- Men's Doubles Semi Final #1 5pm
- Women's Singles Semi Final #1 6pm
- Men's Singles Semi Final #1 7pm
- Mixed Doubles Semi Final #1 8pm
Here apart from the first match, Women's Doubles Semi Final #1, all other times are estimates, and the matches may begin earlier or later than anticipated, accordingly with when the previous match finishes.
This is known as the "Order of Play" and each match will be numbered. Often the time estimates may not even be shown (apart for the first match), just the order in which the matches will proceed.
This is the reason why the game you wanted to watch did not quite appear at the scheduled time.