It's the first time I have to pay the apartment rent myself and I have some doubts about when should I pay it. The lease states:

> 
> ... at the latest of the 5th working day after the commencement of the tenancy in the 30 days rhythm ...
> 
> 
> 

I moved to this apartment on March, 18th, so I'm not sure whether I should consider the 30 days rhythm starting from that day or from the 1st of each month.