A training plan can fit real schedules when it treats calendar availability as an input and moves only the sessions that still make sense after a conflict. Give people a clear rule for what changes, what stays fixed, and when the app asks before reshuffling their week.

A calendar-aware fitness app has two jobs that are easy to conflate: finding a plausible time for the next workout, and keeping the training plan coherent when life changes that time. The second job is where a schedule becomes product behavior instead of a row of calendar blocks.

A builder on r/SideProject described a workout app that reads calendar gaps, offers to move a session when a meeting conflicts, and rebuilds the rest of the week when a workout is missed. The interesting design problem is not simply inserting a workout into an empty slot.…