You have calendars in more than one place, and you want your busy time to show up everywhere so nobody double-books you. Keeper.sh and SyncDate both do that job.
SyncDate wrote a comparison of us first, and it is accurate about most of what we ship. Here is ours, with a link behind every figure.
How fast does a change reach your other calendar?
SyncDate's features page puts the end-to-end result at "roughly 4 seconds" on Google and Outlook.
Keeper.sh reads your calendars every minute, on every plan including Free, and writes the copies out every minute on Pro or every 30 minutes on Free.
So a change reaches your other calendar in about a minute on Pro, two at the outside. On Free it is about fifteen minutes, thirty-one at the outside.
On iCloud, Fastmail and other CalDAV calendars, neither of us is instant. Apple publishes no way for a calendar tool to be told an event changed, so every product in this category checks those calendars on a timer.
What does each one cost?
SyncDate shows annual pricing by default. Their pricing page lists Plus at "$7.42/mo" billed as "$89 billed annually", and Pro at "$14.08/mo" billed as "$169 billed annually". The same page says plans "start at $8.99/month", which suggests month-to-month costs more.
Keeper.sh has one paid plan at $5 per month. There is no seat pricing and no higher tier.
| Keeper.sh | SyncDate | |
|---|---|---|
| Free plan | 2 linked accounts, 3 connections | 2 calendars, 2 accounts, 1 sync setup, 1-month horizon |
| Entry paid plan | $5/month | $7.42/mo billed annually ($89/year) |
| Higher paid plan | None | $14.08/mo billed annually ($169/year) |
| Team plan | None | Custom, minimum 5 seats |
Our free plan sets no limit on calendars per account. Theirs caps you at two calendars and one sync setup, and only looks one month ahead.
A contractor juggling nine client calendars pays the same $5 on Keeper.sh Pro as someone with two.
Which calendars does each one connect?
Both cover the big ones. SyncDate supports Google, Outlook, CalDAV and iCal feeds, and names iCloud, Fastmail, Infomaniak, mailbox.org, Posteo and Nextcloud as CalDAV servers it works with.
Keeper.sh supports Google, Outlook, iCloud, Fastmail and any CalDAV server, and can read and write all five. We also read iCal and ICS links, but cannot write to them, because those links only go one way.
Call this one a tie.
Where Keeper.sh fits better
It is open source. Keeper.sh is AGPL-3.0, so you can read the sync engine before trusting it with your calendar. SyncDate says plainly on their comparison page: "SYNCDATE is not open source and cannot be self-hosted."
You can run it yourself, with every paid feature unlocked. More on that below.
It costs less. $5 a month against $7.42 a month billed annually, and more than that month-to-month.
Your event details stay put by default. Every calendar you connect starts by copying a busy block titled after the calendar it came from, leaving the title, description and location behind. Pro is what shows the real detail.
One calendar feed for everything. Keeper.sh gives you a single private iCal link combining the calendars you choose to include. Paste it into anything that reads calendar feeds for one merged view.
An API and an agent connector on the free plan. Keeper.sh has a REST API, and an MCP server with 14 tools against SyncDate's 12, so tools like Claude can read and change your calendars. Both are capped at 25 requests a day on Free, and uncapped on Pro.
What their comparison gets wrong about our agent tools
Their page calls our agent tools "read-focused (list_calendars, get_events, get_event_count, over OAuth 2.1)". We ship 14 tools and 4 of them write: create_event, update_event, delete_event and rsvp_event. An assistant connected to Keeper.sh can book, edit, cancel and reply to invitations, not just look.
We do not think this was careless. Their page already carries a dated correction retracting an earlier mistake about us, which is more than most companies do.
What SyncDate has that Keeper.sh does not
Speed on Google and Outlook. Roughly 4 seconds end to end, per their features page, covered above.
A signed DPA. SyncDate publishes a self-serve Data Processing Agreement, names its operating company, DUMA DIGITAL SOLUTIONS S.R.L., and lists its subprocessors; Keeper.sh has no such agreement for the hosted service.
Named infrastructure. Hetzner hosting in EU data centres, an ISO 27001 certified management system, and OAuth tokens encrypted at rest.
Running Keeper.sh yourself
Running Keeper.sh yourself gets you the full product. Every Pro feature turns on automatically, including per-minute writes and the uncapped API.
This is the option to take when your data cannot leave your control. You keep the database, the tokens and the logs, and nobody else is in the path to sign an agreement with.
It is real work, though. You need Docker and Docker Compose, a Postgres database, a Redis instance and a domain, plus your own Google and Microsoft applications for calendar access, which is the fiddliest part.
Most people should use hosted Keeper.sh and pay the $5. Self-hosting is there when you need it, and the repository has the full setup guide.
FAQ
Which should I choose?
Keeper.sh, for $5 flat however many calendars you have, event titles stripped by default, and an agent connector at no cost. SyncDate has four-second updates and a signed DPA, which Keeper.sh does not.
Does Keeper.sh really sync every minute?
We read your calendars every minute on all plans, including Free. Writing out is every 30 minutes on Free and every minute on Pro. Comparisons that call Keeper.sh a 30-minute product are describing the free plan's writes.
Can I try both?
Yes. Both have free plans that need no card. Connect one calendar to each and watch how they behave for a week.
Other comparisons
Still weighing tools? These cover the rest of the field.
- Keeper.sh vs CalendarBridge
- Keeper.sh vs Kalender Sync
- Keeper.sh vs Morgen
- Keeper.sh vs OneCal
- Keeper.sh vs Reclaim.ai
- Keeper.sh vs SyncThemCalendars
- Nine calendar sync tools compared on price, speed and privacy
Sources
Everything above about SyncDate comes from their own public pages, checked on the date this post was published:
- syncdate.app/pricing — plans, prices and free tier limits
- syncdate.app/features — supported calendars and the four-second figure
- syncdate.app/mcp — 12 tools
- syncdate.app/security — hosting, encryption and certifications
- syncdate.app/subprocessors — vendor list
- syncdate.app/dpa — the Data Processing Agreement
- syncdate.app/compare/syncdate-vs-keeper — their comparison and correction notice
Prices change. If a figure here is out of date, their page wins, and we would appreciate you telling us.