So I have an interrail pass for 2 continious months. But I am not sure when I can active the pass, and so start the 2 months of traveling.

From the examples on the page, it starts on the first of the month and ends at the last of the other. But can I also start the 2 months in the middle of a month? 16th of June for example? Or does it have to be the first of the month?

Regards!