Most programs start in the afternoon or evening of Day 1 with upon arrival at your first hotel (or the boat). You don't usually ride that day; it's just a time to arrive and relax. Cycling often begins the next morning.
If you're on a guided tour, there's usually a group dinner the first night followed by an orientation. If you've opted for a dinner package, dinner the first evening is generally included.
Depending on when your overseas flight arrives, you may want to arrive in the start city a day earlier. You'll be more relaxed, and you'll have the chance to explore the city on your own.
In exceptional cases, tours include rides on the first day, but these are noted in the Program tab.