What conditions must be met in order to receive a per diem at Jazz? ie Any calendar day where you complete a flying sector?
4 hours of duty, and you'll get a perdiem, even if it's a single-day pairing.
How much you get will depend on how long your duty period is, and checkin/checkout times.
Example, if you do a 10 hour duty period on a single-day pairing, you will get one lunch, one dinner, and one incidental allowance, for a total of $63.98 perdiem.
Now if you do a 4-day pairing that checks in prior to 16:00 local, and checks out after 16:00 local (for calculation purposes), your perdiem will be $298.16.
I should add that meals (snacks) are still brought on board for pilots if you are unable to have a 45-minute break in any 4 hours of duty. So if you do two 2-hour legs with a 44-minute turn you will get fed. This does not affect perdiem rate, you still get paid if you receive an on-board meal (snack).