If I See You Again Tomorrow by Robbie Couch

For some reason, Clark has woken up and relived the same monotonous Monday 309 times. Until Day 310 turns out to be...different. Suddenly, his usual torturous math class is interrupted by an anomaly-a boy he's never seen before in all his previous Mondays.

When shy, reserved Clark decides to throw caution to the wind and join effusive and effervescent Beau on a series of "errands" across the Windy City, he never imagines that anything will really change, because nothing has in such a long time. And he definitely doesn't expect to fall this hard or this fast for someone in just one day.

There's just one how do you build a future with someone if you can never get to tomorrow?