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 is Keeper.sh genuinely 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. Showing the real detail is a choice you make on Pro, not the starting point.
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 so tools like Claude can read and change your calendars. Both are capped at 25 requests a day on Free, and uncapped on Pro.
One correction
Their comparison 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.
Where is SyncDate genuinely better?
A four-second figure on Google and Outlook, published on their features page and covered above.
Paperwork your legal team will ask for. SyncDate publishes a self-serve Data Processing Agreement, names DUMA DIGITAL SOLUTIONS S.R.L. as the operating company, and lists its subprocessors. If your employer needs a signed DPA before you connect a work calendar, that is the shorter route.
Keeper.sh has no such agreement for the hosted service. The answer here is a different shape: run Keeper.sh on your own server, and nobody else is in the path to sign one with.
Named infrastructure and encryption. Their security page states hosting "with Hetzner in EU data centres (Germany and Finland)", running under an ISO 27001 certified management system. The same page says "OAuth tokens are encrypted at rest with AES-256-GCM."
Their MCP server has "12 tools". Keeper.sh ships 14, including triggering a sync, pausing a calendar and finding free time, so an assistant can drive either one.
They disclose their own gaps too, noting they are "not currently SOC 2 or application-layer ISO 27001 certified." Their subprocessor list also names several US vendors alongside the EU hosting. That is normal for a SaaS product and they document it openly, so read the list yourself if data residency is your reason for choosing.
Running Keeper.sh yourself
Self-hosting Keeper.sh is not a stripped-down version. Every Pro feature turns on automatically on your own instance, 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.
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?
Choose SyncDate if you need updates in seconds, or if your company requires a signed DPA. Choose Keeper.sh if you want open source, self-hosting, a lower price, or an API and agent connector without paying.
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.
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.