you can start the pill any day of the week.
The 1st of June can be on any day of the week.
Sunday is the first day of the week. See the related question below for the reasons why.
Monday is the first day of the school week (in the US).Most schools start their week on Monday.
If you mean what day of the week did July begin, the 1st of July 2013 was a Monday.
It started on a Friday.