To make calendar sharing secure, our native iOS app uses the EventKit library to sync events from multiple calendars (Apple, Outlook, etc) to your TRMNL account.
(If you use Google Calendar, check out our native Google Calendar plugin)
Set up the application
Follow the steps below to get up and running in a few minutes.
Step 0 - Get TestFlight
While this app is in beta, Apple requires testers to install their "TestFlight" app:
https://apps.apple.com/us/app/testflight/id899247664
Step 1 - Get the app
From an iOS device, visit the URL below and accept the TestFlight invitation:
Step 2 - create a Calendar plugin
Inside TRMNL, navigate to Plugins and create (or update) an existing Calendar* instance with a "Data Provider" value of "iPhone App" at the top of the settings form.
You may set up multiple calendars, each with their own settings.
* Apple, Outlook, Fastmail, Nextcloud, CalDAV
Step 3 - Sync your calendars
Inside the TRMNL Companion iOS App, pull down on the "Sync" tab to refresh the Calendar Mappings section. Select the Calendar plugin instance(s) you set up in Step 2 and sync as many calendars as you'd like.
It's OK to mix and match providers. For example you could sync a personal Google Calendar and a work-only Outlook calendar. The calendars themselves will not be shared -- rather, their events will be pulled independently and synced with your TRMNL account.
Step 4 - You're done!
Going forward, calendar events should automatically sync in the background via the TRMNL companion iOS app.
Customize your sync experience
By default, TRMNL Companion will sync new calendar automatically in the background. But this may functionality may be paused if you "force close" the application.
If you'd like to increase the sync frequency, set up an Apple Shortcut as follows.
Step 1 - Create a Shortcut
Open the Shortcuts app on your iPhone. Click the "+" symbol to add a new Shortcut. Search for "TRMNL" and select the TRMNL Companion app.
Step 2 - Enable the Shortcut
After selecting the TRMNL Companion app, tap the Sync Calendar option. On the next screen we suggest disabling the "Show When Run" toggle.
If you'd like to test this out, tap the ▶ (play) icon on the bottom right corner.
Step 3 - Automate the Shortcut
Tap the back button in the top left of your Shortcuts app to return to your home screen. Next, tap Automation in the bottom menu.
Here you can set up a schedule, combining a time of day with the Sync Calendar Shortcut we created a moment ago. Click the image below to see it expanded.
Note our recommendation to set "Run immediately" and disable "Notify when run," which will otherwise create a banner notification on your home screen.
Troubleshooting
As of October 2025, this feature is in beta. Please send feedback to ryan@usetrmnl.com.
Security
TRMNL Companion uses EventKit to fetch only the details need to populate a calendar -- an event's title, description, start/end time, status, and calendar name. hackers are welcome to Man-In-The-Middle the network request:
{
"end" => "18:00",
"start" => "16:00",
"status" => "accepted",
"all_day" => false,
"calname" => "ryan@usetrmnl",
"summary" => "Support chats",
"end_full" => "2025-10-02T18:00:00.000Z",
"date_time" => "2025-10-02T16:00:00.000Z",
"start_full" => "2025-10-02T16:00:00.000Z",
"description" => "Respond to customers from my walking standup desk"
}
TRMNL Companion also only retrieves events from the past 7 days, to the next 30 days.