Daytime v night owl data for existing connections

Hi There,
Just a question regarding open connections etc.
If i open my connection on the last day of the month at say 11pm, but i only schedule downloading to start happening after midnight [which will then be the next day of the next month of course], then which cap is used ? data of the month I opened the connection in or the following months data?. Cant seem to find any info that answers this question.

Regards