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Updates are partial. Pass the event’s uid plus only the fields you want to change; every field you omit keeps its stored value. Rescheduling a meeting is uid + start. Renaming one is uid + title; to rename a calendar itself, use update_calendar. To put an event on a different calendar, use move_calendar_events. Nothing you don’t mention is touched — a recurring series stays recurring, attendees invited elsewhere stay invited, the location survives. There is no full-replacement mode. Because omission means “keep”, clearing a field needs an explicit empty value: A call that names no changeable field at all (just a uid) is rejected. Times. An explicit end always wins. Omitting end while moving start keeps the event’s stored duration — “push the standup an hour later” is a two-field call and won’t silently stretch the meeting. Omitting both keeps the stored time. All-day events. A partial edit keeps an all-day event all-day: renaming it or changing its reminder leaves its dates alone, and a date-only start moves it while keeping its length in days. To switch an event between all-day and timed, pass both start and end, as dates (end exclusive) or as date-times. With only one of them, the other side’s clock time or length would have to be made up, so the edit is refused. timeZone does not affect all-day dates. Reminders. Reminders the event already has, including ones written by another client, carry over unchanged unless you pass reminderMinutesBefore. A number replaces all of them with one reminder, and "none" removes them. A call that changes only the reminder edits the reminders in place: attendees keep their responses and are not notified. On a series, that replaces the reminder on every occurrence, including ones you changed individually. To change one occurrence’s reminder, pass its recurrenceId. On a series with attendees, that works only once the occurrence has individual changes, because creating them would reset the attendees’ responses to it. Attendees. attendees replaces the whole list. addedAttendees / removedAttendees change specific addresses against the stored list instead, so you can drop one person without reading the list back first. They cannot be combined with attendees. One occurrence. Pass recurrenceId (the occurrence’s original start) to change a single occurrence of a repeating series; the master rule and every other occurrence stay unchanged. Omitted fields merge against that occurrence’s stored state — an override you wrote earlier if there is one, otherwise the occurrence’s own slot — so re-editing a moved occurrence never drags it back to the series’ time. Attendee deltas cannot be combined with recurrenceId (membership is a property of the series). By default the attendees are re-notified by iMIP. Pass notify: "none" to make the edit silent — useful for a trivial change such as dropping your own duplicate address.

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Parameters

All parameters of create_calendar_event, each of them optional here, plus the fields below.
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string
required
The event’s iCalendar UID, from create_calendar_event or list_calendar_events. Up to 255 characters; must not contain path separators.
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string[]
The complete attendee list after the edit, replacing the stored one. [] uninvites everyone and turns the event into a personal one. Omit to keep the stored attendees.
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string[]
Email addresses to invite on top of the stored attendees. Cannot be combined with attendees.
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string[]
Email addresses to uninvite, matched case-insensitively against the stored attendees. Removing an address that isn’t invited is a no-op. Cannot be combined with attendees.
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string | object
New repeat rule for the whole series, in the same shape create_calendar_event takes. The literal string "none" collapses the series to a single event. Omit to keep the stored rule.
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string
default:"all"
all re-sends invitations/updates to the attendees; none makes the edit silent (the attendees on the event are not notified). A removed attendee may still receive a cancellation.
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string
ISO 8601 instant naming one occurrence of a repeating series (its original start) to change in isolation. For an all-day series, the occurrence’s date (2026-06-23). Cannot be combined with recurrence or with attendee deltas.
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integer | "none"
Replaces every stored reminder with one that fires this many minutes before the start. "none" removes all reminders. Omit to keep the stored ones.

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Examples

Reschedule a meeting an hour later, keeping its length, attendees, title and recurrence:
Call
Result
Remove one attendee from a recurring meeting, quietly, re-passing nothing else:
Call
Result
Move one occurrence of a weekly series without touching the rest:
Call
Result

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Errors

  • Nothing to update: … — the call named no changeable field.
  • Event not found: <uid> — no event with that UID in the target calendar.
  • Event end must be after its start. Nothing was changed.
  • Calendar not found: <url> — the calendarUrl didn’t resolve.
  • Removing those attendees would leave the event with none. — a delta removed the last attendee. To strip every attendee deliberately, pass attendees: [] instead.
  • recurrenceId … does not match an occurrence of this series — the instant must equal an occurrence’s original start (its date, for an all-day series).
  • This series is not all-day; pass recurrenceId as the occurrence's original start date-time … — a date recurrenceId on a timed series.
  • This series is all-day; pass recurrenceId as the occurrence's date … — a date-time recurrenceId on an all-day series. It is refused, not truncated, because a date-time’s calendar day depends on its offset.
  • To switch an event between all-day and timed, pass both start and end … — only one of them was passed, in the other kind.
  • Pass `start` and `end` both as dates … or both as date-times … — a date mixed with a date-time.
  • An all-day event's `end` is exclusive … — an all-day end on or before its start. The message names the right end.
  • The occurrence on <recurrenceId> was cancelled, so there is nothing to edit. Nothing was changed. — the occurrence was cancelled with delete_calendar_event, so an override for it would be an orphan the series never shows.
Because an edit rebuilds the event from its stored state, it refuses (with a clear message, changing nothing) when that state can’t be reproduced faithfully:
  • Individually-customized occurrences. A whole-event edit would flatten them. Edit the occurrence directly with recurrenceId, or re-specify the whole event (start, end, title, attendees and recurrence) to deliberately replace the series — note that this escape hatch does discard the customizations.
  • Cancelled occurrences. A series with an occurrence cancelled via delete_calendar_event can’t be edited as a whole event: the rebuild would restore the cancelled instance and re-invite everyone to it.
  • An attendee stored in a non-email address format. Pass the complete attendees list instead.
  • An event stored with a DURATION and no end. Pass start and end.
  • A moved series that contradicts its repeat rule. Moving start onto a weekday the kept rule doesn’t list (e.g. a Friday under BYDAY=TU) would add one occurrence rather than move the series. Pass recurrence with the new rule as well.

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What an edit still does not preserve

A whole-event edit rebuilds the VEVENT, which resets attendee response status (PARTSTAT) to needs-action. This predates partial updates and applies to every edit, including a one-field one. Reminders (VALARM) are carried over unchanged.