Preview and edit school timetable calendar files (.ics) in your browser

Most timetabling systems can export a school timetable as calendar files, often one per class, teacher or room, so lessons show up in Google Calendar or Outlook. Such a file is plain text in the iCalendar format (RFC 5545). Each event is a VEVENT block with a start (DTSTART), an end (DTEND or DURATION), a title (SUMMARY) and optional fields such as LOCATION, RESOURCES, ATTENDEE, ORGANIZER and CATEGORIES. The tool reads those fields directly. It never guesses a teacher or a room from the words in a title.

Repeating events carry a rule (RRULE) instead of a list of dates. The tool expands daily, weekly, monthly and yearly rules into dated occurrences in the event's own time zone, so a 09:00 lesson stays at 09:00 after the clocks change. Dates listed in EXDATE are left out, and a moved occurrence (a second VEVENT with the same UID and a RECURRENCE-ID) replaces the date it was moved from.

A double booking is two events at overlapping times that list the same teacher, room or group in RESOURCES, or the same attendee. An event with no RESOURCES books its LOCATION instead. All-day events, cancelled events and events marked as free do not count. One lesson written several times, once per group or per teacher calendar as timetabling systems export it, is one booking: copies with the same times and the same course (or title) never clash with each other.

When you save an edit, only the lines you changed are rewritten. Every other line of the file, including reminders, time zone definitions and custom X- fields, is written back exactly as it was read. The edited event gets a higher SEQUENCE and a new DTSTAMP, which is how the iCalendar standard marks a revised version of the same event. For a repeating event you choose the scope, as in Google Calendar or Outlook: this event (an override with RECURRENCE-ID), this and following events (the series ends with UNTIL and a new series starts), or all events (the series moves, and its exception dates move with it).

Select Try with a sample. The sample is an invented school week: three groups (7A, 7B and 8A), six teachers and six rooms, with each lesson written as a weekly repeating event whose RESOURCES field lists the teacher, the room and the group.

The clash panel reports one double booking. On Thursday, Maria Lopez is on exam supervision from 10:30 to 11:15 while she teaches History to 7A from 10:15 to 11:00. Select the clash to jump to Thursday, then drag the supervision down to 11:30. The warning disappears, because she has no lesson at 11:30.

Wednesday shows a lesson that had already moved: 7B's Science lesson runs at 13:00 this week instead of 09:15, written in the file as an override of the weekly series. Filter by Science lab to see the room's week, or by Maria Lopez to see hers.

Open Download. The summary lists one moved event. The downloaded file is the sample with that one event changed: new DTSTART and DTEND lines, SEQUENCE raised from 0 to 1, and a new DTSTAMP.

It edits a copy of your timetable calendar file. It does not connect back to your timetabling system, Google Calendar or Outlook, so a subscribed calendar feed keeps showing the old events until you import the new file, and attendees get no update emails.

It finds double bookings but does not resolve them. Moving a lesson to a free slot is up to you, one event at a time, and nothing checks teacher working hours, room capacity or which groups share students.

Files are capped at 1 MB each and 8 MB together. A rule that repeats without an end date is shown for two years from its start, and rules that repeat hourly or more often show only their first occurrence. Both are written back unchanged.

Automatic school timetabling in Smootables starts where this tool stops. Its import page reads the same calendar files, the solver places every lesson against teacher, room and group constraints, and the finished timetable exports back to ICS for each teacher, group or room.