The native iOS calendar doesn't have a useful URL scheme that you could use to do this... However, the 'Fantastical 2' app does, and it is always in sync with the native calendar. Using Fantastical's URL scheme you can add events to the calendar.
For example, you would be able to use the 'Open URL' script step to to go to the following URL:
"fantastical2://parse?title=" & myTitleField & "&start=" & MyStartField & "&end=" & MyEndField
For more details on the Fantastical URL scheme have a look here: https://flexibits.com/fantastical-iphone/faq
It also allows you to add all day events etc...
Hope this helps :-)
Filemaker can create an .ics file but FMGO does not appear to be able to send it to the calendars. FMGO can send the .ics file to your email and then the email tapping on the attached ics file can send the event to your calendar. If you are interested in this option there is more info at
To my knowledge, the only direct way to communicate from FM Go with other apps is through the app's custom URL scheme. Calendar has one "calshow://", but it is undocumented and not listed by apple as a legal way to interact with the app (the only legal ways to interact with the app are using Swift or Objective-C languages). So, other than opening the app via the script step Open URL:[calshow://], I don't know how you would create, update and delete events.
Alternatively, you might research an app called Workflow that automates things you want to do on your iOS device and somehow "glues" all the apps it can access together. In the Workflow app, you will need to create a workflow that calls the Calendar app and creates the event, then using the Workflow url scheme (workflow://) call the workflow you created from FM Go. THIS is something that I never tried though but it seems doable. So if, you manage to do it, it would be great if you give us some feedback and lessons-learned.
Edit : ----
While I was writing my own reply, Skywilmot posted a simpler alternative using the Fantastic 2 app. For the problem at hand, it seems less of a hassle than using Workflow.
That is a great solution for this particular problem skywillmott.
I did not know about this app. Thanks for enlightening us.