How to add repeating event in calendar

Running OC 9.1.1 on CentOS. I want to set an event in the Calendar app to repeat on the first Sunday of every month. It is not clear how I should enter this. In the 'repeating' tab, when I set 'repeat' to 'every month' and 'repeat every' to 1, it uses the date instead of the day of the month to calculate the repeat instances.

Is there documentation on how to specify repeat every 'first Sunday' or 'second Tuesday' [for example] of each month?

Seems like this used to work in an earlier version of OC [before Calendar got rewritten].