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How lessons are generated from a timetable

Understand when GapFiller creates lessons from your timetable, how holidays are skipped, and what happens when you edit or delete slots and dates.

4 min readUpdated July 30, 2026

By the end of this guide you'll know when GapFiller creates lessons from a timetable, what those lessons look like, and how edits and holidays affect them.

There is no “Generate” button

Lesson creation from a timetable is automatic. You won't find a separate Generate Lessons control in School Settings.

Generation runs when:

ActionResult
You create a timetable that already has slotsLessons are created for the whole date range
You Add Slot on an existing timetableLessons are created for that slot across the date range
You finish onboarding with timetables set upLessons are created for all your timetables

Creating a timetable without slots creates no lessons yet — add slots when you're ready.

Duplicating a slot copies the slot pattern. If lessons don't appear for the new slot as you expect, check the slot details or add the meeting as a new slot with Add Slot.

What gets created

For each slot and each matching weekday between the timetable Start Date and End Date, GapFiller creates a lesson on the calendar, for example titled like Math - 3A.

Each lesson is linked to the timetable and slot, so later changes can update them together.

After a timetable has slots, matching days in the date range show up as lessons on the calendar

These lessons start empty of plans and materials. Fill them by hand, or apply curriculum content so each date gets the right topic.

Holidays are skipped

If a day falls on a school holiday, GapFiller does not create a lesson for that date.

Set holidays under School → School Settings → Academic Calendar.

Holidays under Academic Calendar are skipped when lessons are generated

Term dates help with planning stats elsewhere in the app; they are not used as the holiday skip list for generation. Put closed days in holidays if you want them excluded.

When you change the timetable

Edit timetable details or dates

When you change school, subject, class or the date range, GapFiller asks:

  • Update All Lessons — apply changes to every linked lesson (including past). Shrinking the range can remove out-of-range lessons; extending it can add new ones (still holiday-aware).
  • Update Future Lessons Only — keep past lessons as they were; update or add from today onward.

Prefer future only when you want to preserve history.

When you change a timetable, choose whether to update all lessons or only future ones

Edit a slot (day or times)

You'll see a similar choice:

  • Update all lessons — new times on every lesson from that slot
  • Update future lessons only — past occurrences keep old times

Delete a slot or timetable

You'll choose whether to delete all linked lessons or future ones only. Past lessons can stay on the calendar if you pick future-only.

Timetable vs calendar vs curriculum

PieceJob
TimetableWeekly rhythm + date range → creates empty dated lessons
CalendarSee and edit those lessons; reschedule one occurrence
CurriculumReusable topics, plans and files → apply onto lessons

Dragging a lesson on the calendar moves that occurrence. It does not rewrite the weekly timetable. To change every Monday permanently, edit the slot.

You can also create a single lesson by hand; GapFiller may offer to link it to a matching timetable.

Practical tips

  1. Set holidays before generating a long year — fewer lessons to clean up later
  2. Use one timetable per school + subject + class (or clear naming if you split terms)
  3. After lessons exist, use Update Future Lessons Only for routine time changes
  4. Fill content with a curriculum apply, or import last year's lessons into a curriculum and apply forward

What's next?

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