android - purchaseTime in subscription with in app billing -

i using subscription inapp billing , wondering purchase time in this

purchase mypurchase = inventory.getpurchase(my_sky); mypurchase.getpurchasetime(); 

what purchase time when subscription used? first date user subscribed product or date of renewal of recent payment?

please thank you

my experience purchase time date first time user made purchase. not updated when subscription renewed.

in my app tell user when next renewal date coming up. add months since purchasetime date , present user.