The activation date is the start of the validity period, there's some confusion going on and you're not the only one.

No matter which pass you choose the validity period will start on 1st June. You don't have to travel that day but you won't be able to travel after 31st July with a 2 months pass.

If you wish to travel in August don't get an expensive 3 months continuous pass (valid until 31st August in that case), wait for a likely 10% discount around New Year.

Many thanks for this reply. It makes sense. You just saved me from buying a dud pass.