Flutter App Uses Bitmask Logic to Solve Timezone-Safe Booking Slot Availability

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A developer building Drivers Lesson, a driving instructor booking app, faced complex scheduling challenges involving recurring availability, multiple block types, and timezone mismatches. Instead of using a list of 48 booleans per day, the developer represented each day's slot availability as a single integer bitmask, enabling fast bitwise operations to merge and filter slots. When an 'extra sessions' feature was added, availability data from two separate API sources had to be merged and deduplicated before being shown to users. A timezone bug — where slots generated in an instructor's local time landed on a different calendar date for students — was fixed by storing and comparing all slots in UTC internally. The final mask logic sits behind a Riverpod provider, exposing only a clean availability result to the UI without exposing the underlying complexity.

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