Prerequisites
- Create an App Password — You need an app password first
Set Up Calendar Sync on Android
A helper app, the permissions Android needs, and then your Zyntro account.
Before You Begin
- An app password, and the Base URL (Android / Thunderbird) address
- The email address you use for Zyntro
- DAVx5 from the Play Store, which is what performs the sync
Android's calendar does not speak this protocol by itself, so it needs a small helper app called DAVx5 from the Play Store. Once set up it runs quietly in the background and you can forget about it.
Most of the setup is not about Zyntro at all — it is granting DAVx5 the permissions Android needs, and telling Android not to pause it to save battery. That last part matters more than it sounds: without it, sync stops at unpredictable times and the symptom looks like a broken connection.
Use the Base URL (Android / Thunderbird) form of the address — the full link including https://, not the bare name.
Steps
Install and open DAVx5
Get DAVx5 from Google Play and open it. The first run walks through a short setup.
On the tasks screen, tick I don't need tasks support and continue — you are syncing calendars, not tasks.
Allow calendar access
On the Permissions screen, tap Keep permissions to open App info. Tap Permissions, then Calendar, and choose Allow.
Without this DAVx5 can connect to Zyntro perfectly well and still show you nothing, because it cannot write to the phone's calendar.
Allow notifications
Back in App info, open Notifications and switch on Allow notifications.
This is how the app tells you when a sync fails, which is the difference between noticing a problem and silently missing bookings.
Keep sync running
Return to DAVx5 and continue. Turn on regular sync intervals, and when Android asks whether to stop optimising battery usage for the app, tap OK.
Android will otherwise pause the app to save power, and sync stops at times you cannot predict. This step is the one most worth not skipping.
Confirm the backup reminder
Tick I already have a working backup strategy and continue. This is DAVx5 reminding you that calendar data is worth backing up — nothing to configure.
Add your Zyntro account
Now add the account itself. In DAVx5, add a new account and choose to log in with a URL and username, then enter:
- Base URL — the Base URL (Android / Thunderbird) address from Zyntro, the full link.
- Username — the email address you use for Zyntro.
- Password — your app password.
Tap Login. When the account has been created, open it and tick the calendars you want on your phone — nothing syncs until you choose at least one.
Result
Your Zyntro calendars are in your Android calendar app, syncing both ways in the background.
Anything you add on the phone blocks that time in Zyntro, so your availability reflects your real week without any effort from you.
Warning: If sync stops working after a few days, suspect battery optimisation. Android sometimes re-applies power saving to apps after an update or a period of disuse. Allowing the app to run in the background again restores it, and no Zyntro settings need changing.
