When I set an event in fullcalendar how do I remove this gap on the right

override this style

.fc-direction-ltr .fc-timegrid-col-events { margin: 0 2.5% 0 2px; }

either match the left and right gaps

.fc-direction-ltr .fc-timegrid-col-events { margin: 0 2px 0 2px; }

or have no gaps at all

.fc-direction-ltr .fc-timegrid-col-events { margin: 0; }

make it day specific by changing to

.fc-timeGridDay-view .fc-timegrid-col-events { margin: 0; }

Correct for FullCalendar v5

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update, this should work for v4

override this

.fc-ltr .fc-time-grid .fc-event-container { margin: 0 2.5% 0 2px; }

to either match left and right

.fc-ltr .fc-time-grid .fc-event-container { margin: 0 2px 0 2px; }

or no gaps at all

.fc-ltr .fc-time-grid .fc-event-container { margin: 0; }