Compared August 2026 · every price and feature below was checked against inovex/CalendarSync’s own site on 28 August 2026. These change — check the inovex/CalendarSync site before deciding.
A free, open-source Go CLI that keeps your calendar data off other people's servers.
CalendarSync keeps your calendar data off other people’s servers — as do the on-device Apple apps compared here. What makes it unusual in that group is that it is a stateless MIT-licensed Go CLI: you write a sync.yaml, run the binary, and it runs anywhere Go does.
The dividing line is Apple. CalendarSync's adapters are Google, Outlook and ZEP for sources, and Google and Outlook for destinations. There is no iCloud adapter and no CalDAV adapter. If the calendar you need mirrored is an iCloud calendar or a subscribed ICS feed, CalendarSync cannot reach it and Calendar Mirror is built for nothing else.
| Calendar Mirror | inovex/CalendarSync | |
|---|---|---|
| Price | $2.99 once · free from source | Free |
| Licence | MIT | MIT |
| Where your calendar goes | Nowhere. It never leaves the device. | Nowhere — it runs locally |
| Credentials | None — it reads calendars the OS has already set up | OAuth tokens for Google / Microsoft, held locally |
| Sources | Anything the device can see — iCloud, Google, Exchange, CalDAV, subscribed ICS feeds | Google, Outlook, ZEP |
| Destinations | Any calendar the device can write to | Google, Outlook |
| Apple / iCloud | Yes — this is the point | No adapter |
| Interface | Menu-bar app on Mac, a normal app on iPhone and iPad | Command line, configured in sync.yaml |
| Scheduling | Built in — a background daemon on macOS, or realtime | None built in; use cron or a timer |
| Title prefix | Yes | Yes — the PrefixTitle transformer |
| Filters | Declined, unanswered, cancelled, all-day, free, duration bounds, title, time-of-day and weekday window | Declined events, all-day, time-based, regex title match |
| Duration filters | Yes | Not published |
CalendarSync’s adapters are Google, Outlook and ZEP. There is no iCloud adapter, so an iCloud calendar is simply out of reach for it.
Calendar Mirror can be the missing adapter. Mirror the iCloud calendar into a Google or Outlook calendar on your Mac, and CalendarSync treats it as an ordinary source from there. You keep CalendarSync’s YAML config and its Linux-friendly scheduling, and you get Apple calendars into it without waiting for an adapter that may never be written.
Bridging adds a hop: Calendar Mirror writes the copy on your device, and the other service then reads that copy on its own schedule. It needs the destination account set up on your Mac or iPhone, and the copy is one-way, like every Calendar Mirror mirror.
None of these are coming later. If you need one of them, buy something else:
One purchase covers iPhone, iPad and Mac. Calendar Mirror is not affiliated with inovex/CalendarSync in any way, and this page is written by Calendar Mirror’s author.