An event belongs to one product
The edit happens where the entity was created: leave in HR, a hearing in legal. The Calendar keeps no second copy of the fact and cannot drift from it.
The Calendar is packaged as a standalone product, but it works as a platform foundation: the same role the file layer plays for the suite.
Without one, every product grows its own date field, its own recurrence logic, its own reminders and its own take on time zones. Recurrence parsing written five times means five different sets of bugs on the day the clocks change.
The Calendar takes that work off the products and leaves them what they really own: the meaning of the event. In exchange it takes on everything to do with time and does it the same way for everyone.

The edit happens where the entity was created: leave in HR, a hearing in legal. The Calendar keeps no second copy of the fact and cannot drift from it.
The product reports a change the moment it happens. An open tab refreshes instantly, nobody triggers a sync by hand.
An event keeps the moment and the zone it originated in. A daylight saving shift in one country does not move a meeting in another employee calendar.
If an event is changed from two devices at once, no edit disappears unnoticed. The person is shown both versions and asked to pick the right one.
Two-way synchronisation with external calendars, shared and resource calendars, slot finding are parts of the product, not a separate add-on.
The Calendar does not connect to external video services and does not parse personal mail looking for bookings. Video meetings are covered by A3.Meet, and the Calendar has no access to mail outside A3.Mail.
A3.Calendar is built by A3.Solutions alongside the rest of the suite: the A3.ID single sign-on, document management, HR, legal and finance products.