JR east pass

Hi there,

Taken from the official website:
Flexible five-day pass: you can use the pass on any five days within a 14-day period starting with the date of purchase or exchange in Japan. You do not have to determine your 5 travel dates at the time of purchase or exchange. For example, if you purchase your pass or get it by exchange on August 1, you can show the pass at a station on any five days between August 1 and August 14 and it will be stamped as valid for use on that day.

Hope that helps,
Daniel