What I did: I tried to set Sunday as the start day for a week.
What happened: I can’t find how to do it. My iOS system settings are week starts on Sunday and all my other calenders on my device start on Sunday. Agenda is the exception.
What I expected: The week to start on a Sunday (not Monday)
Things that might be helpful to know (Agenda version, OS and model, etc): Agenda 1.3 on iPad and iPhone running iOS 11.4.