Manual method
Export individual Mac calendars as .ics and, optionally, preserve a separate Calendar Archive (.icbu).
- In Calendar on Mac, show the calendar list and select the calendar to preserve.
- Choose File → Export → Export and save the .ics file in your archive.
- Repeat for each relevant calendar and label the account it came from.
- Optionally use File → Export → Calendar Archive for an additional app-specific archive.
Coverage and limitations: An .icbu restore replaces current calendar data, so do not test it against your live calendar. The .ics route is more portable. Account synchronization and provider retention affect what is present locally; inspect historical coverage.
Size and time to allow
Illustrative small / central / large case: 0.001 / 0.02 / 0.2 GB (decimal GB). These are planning assumptions, not a measured average per person. 20 MB is an illustrative long-running calendar history with descriptions, not a population average.
Preparation: No provider export queue for the Mac route. Allow 1–5 minutes for selection and small exports as an estimate; refresh/synchronization may take longer.
For the central 0.02 GB example, network transfer alone is approximately:
| Connection | Estimated transfer |
|---|---|
| 10 Mbps | 23 seconds |
| 50 Mbps | 5 seconds |
| 100 Mbps | 2 seconds |
Assumes 70% sustained use of the stated connection. Provider throttling, many small files, retries, local extraction and copying add time. For online backup use your upload speed. These are not estimates of the provider’s preparation queue. See calculation and large-file advice.
Store and verify the archive
The example is small enough for an encrypted USB key, external drive or private cloud folder. Choose a second independent copy as well; a single USB key is easy to lose and a sync folder alone can propagate deletion.
Create apple_calendar/YYYY-MM-DD/originals/, preserve the untouched download, and extract a separate working copy when needed. Allow extra free space for archive plus extraction; compressed text can expand far beyond twice its size. Record account/scope, export date, date coverage and missing items in a local README without passwords.
Check several old and recurring events in a separate viewer or disposable calendar and preserve source time-zone information. Reopen a sample from the second copy before deleting or replacing any source. Storage choices and verification.
Sources and review
Public documentation was reviewed on 27 October 2026. No signed-in export or restoration was performed. Account options and availability can change; follow the current provider instructions.