Field rules
Every other sync tool gives you a setting. This gives you a rule.
A setting applies to every event in the sync. A rule reads the event first, then decides what the copy should say.
Why one setting isn't enough
Most sync tools let you choose, once per sync, what crosses: keep the title or replace it with "Busy", carry the description or drop it. That's a fine answer when every event deserves the same treatment.
It stops working the moment they don't. If you advise two clients in the same market, "Vendor selection — datastore" cannot cross with its title intact. But your own team's standup, in that same calendar, is useless as an anonymous grey block.
One setting forces the stricter answer onto everything. The calendar becomes a wall of "Busy" — technically private, practically unreadable.
The setting you already know is just the first rule
Here's the blunt instrument every tool offers, written as a twocal rule. No condition, so it matches everything:
Writing to · Work calendar (Microsoft)
Now give it a condition and it stops applying to everything. Conditions read the event on the source calendar; the action writes to the copy on the destination.
Writing to · Work calendar (Microsoft)
Writing to · Work calendar (Microsoft)
Writing to · Personal calendar (Google)
One rule makes one change. Stack them for more — they run top to bottom, and the editor tells you when a later rule has made an earlier one dead rather than letting it sit there looking active.
You can see the result before you trust it
Every sync pair carries a What crosses over panel. It reads your rules and reports, field by field, what the other calendar will actually show — and it's there before you write a single rule, so the default is never a mystery either.
What crosses over
On Work calendar you'll see
Three states at a glance: carried as-is, dropped, or transformed and shown with the value it will be given. Time and recurrence are always synced — the one thing no rule touches, because it's what makes the copy a real event rather than a note.
Two rows are always dropped, whatever your rules say. Attendees never cross — a copy that invited people would send them a second invitation from a calendar they never agreed to. Reminders never cross either. The panel says so plainly rather than implying a propagation that doesn't happen.
What you can match on
Conditions read the source event as it really is, before anything is hidden or modified.
Any source calendar
Google, Microsoft, iCloud, ICS
Provider-specific
Offered only when that provider is the source
Operators follow the field's type: equals, contains and matches regex for text; greater than, at least, less than, at most for numbers — each with its negative.
What you can set
Actions write to the copy. The editor only offers what the destination can hold.
Any destination
Google, Microsoft, iCloud
Provider-native
In that provider's own vocabulary
Every action is set or clear. Clearing is how you drop a field for the events a rule matches, rather than for all of them.
No lossy translation
Microsoft has an Out of office status and a Working elsewhere status. Google has neither — it has Free and Busy. Google has eleven named event colors; Microsoft has categories, a different idea wearing similar clothes.
A tool that offers one blended vocabulary across providers has to guess a mapping, and the guess is wrong often enough to matter. We don't offer a field the destination can't hold. Writing to Microsoft, you get Microsoft's statuses by their real names. Writing to Google, you don't — because they don't exist there.
Fewer options in the editor, deliberately. Everything offered lands exactly as shown.
Where to find it
Open a sync pair and scroll to the calendar being written to. Rules are set per direction, so a two-way pair gets two independent sets — you're always answering one question:what should this calendar see?
twocal owns the fields a rule sets. Edit one by hand on the copy and the next sync puts it back; the editor says so rather than letting you find out.
Try it on one calendar first
14 days free, no credit card. Add a pair, write one rule, and check the panel before you trust it.