If you are 25 at the first date of validity of your ticket...
07-03-2006 - 17:35
if you are 25 at the first date of validity of your ticket, you will get the under 26 interrail ticket.
example: the day when you get 26 years old is the 15th July 2006 and you buy the ticket before with a date of depature for example the 14th July 2006 printed on the ticket, you will get the under 26 ticket. If you buy the ticket on the 16th July 2006, you have to pay the expensive one...