Rent is usually paid per calender month which means if the tenancy starts on the 29th July, the rental period runs from 29th July to 28th August. The rent payment is then paid on the 29th of every month.
In general, is there a defined process for what happens at the end of February in each non-leap year when the rental period start date is 29, 30 or 31 of a month?
Nothing happens, as the monthly rental is fixed regardless of whether a month has 28, 29, 30 or 31 days in it. It is a monthly rental premium, regardless of the length of the month.