snapToGridGranularity property
When resizing, the event end is snapped to an imaginary grid, for better user experience. This variable controls the granularity of that grid, which defaults to 15 minutes (that is, events will be snapped to clock times ending in :00, :15, :30 and :45). To disable this snap, set this value to Duration.zero.
Implementation
final Duration snapToGridGranularity;