Many people live in two systems. The company runs Exchange or Microsoft 365, while a partner, a client or a side project uses Google. The result is a calendar nobody trusts, and the first double booking usually happens in front of a customer. Here is how to stop double booking for good.

Why clashes happen

Each calendar only knows its own events. A call booked in Gmail is invisible in Outlook, and the other way round. People copy meetings by hand to be safe, and copies are always late. The more people share meetings across systems, the more the copies drift.

What a good sync does

• Copies events in the direction you choose: one way, the other way or both.
• Works for the people who need it, not for the whole company by default.
• Connects the systems you really use. AddSync Calendar covers Exchange Server 2016, 2019 and SE, Microsoft 365, Google, Outlook.com, Apple Calendar, HCL Domino and CalDAV.
• Carries Zoom links along with the meeting.

Decide the rules first

1. Choose the master calendarPick the system that wins when two entries disagree. For most companies it is Exchange or Microsoft 365.
2. Choose the directionTwo-way for people who work in both systems. One-way when a calendar should only receive, for example private meetings that must stay out of the work calendar.
3. Choose who is inAdd the people who really live in two systems first. Others can follow.
4. Name a contactSomeone who handles questions when a meeting looks wrong.

Example: a week with and without sync

Example, not a real customer. Acme works in Exchange, and the sales team works in Gmail because most clients do. On Monday Olivia books a client call for 14:00 in Google Calendar. Without sync, Liam in Exchange cannot see it and books a review at the same time. With sync he sees Olivia busy at 14:00 and moves his review to 15:00.

Nothing clever happened. Two calendars simply agreed.

Check it with a test week

Create an event on each side and change it. Move it, shorten it, cancel it. Confirm that edits and deletions follow in the direction you chose. Ask two people to book each other across systems and see whether the free time looks right. Then roll it out to the team.

Common mistakes

• Syncing everyone at once instead of the people who really live in two systems.
• Choosing two-way sync without deciding which calendar wins.
• Skipping the test week and finding problems in front of a customer.
• Forgetting recurring meetings, which behave differently from single events.
• Not telling people which calendar to trust.

How people join

You add people one by one or import a list, up to the number of licenses you bought. You can send an optional email invite. Each person signs in once with their own Microsoft or Google account, so nobody collects passwords. See the pages on Google Calendar sync and Microsoft 365 sync for the details.

Questions and answers

Can I sync in one direction only?

Yes. You choose one way, the other way or both ways for every source.

Is it only for Exchange and Gmail?

No. It also connects Microsoft 365, Outlook.com, Apple Calendar (iCloud), HCL Domino and CalDAV.

What if only a few people use Google in a Microsoft company?

That is a common setup. The few in Google Calendar and the rest in Exchange or Microsoft 365 see the same meetings.

Is it for private users?

No. AddSync is built for businesses and IT teams, and your administrator sets up the connection.

Written by the AddSync team.