Just wondering ^^

generated pets start life at the beginning of adolescence- 216 maturity hours- and will reach adulthood at 648 maturity hours. That is, it will take them 18 days.
You can see how old generated and genetested pets are exactly up until they hit adulthood by looking at the bit in their profile labelled 'Maturity'- in untested pets, it just tells you what life stage they're at, but if generated/tested it will look something like this:
"Maturity: Adolescent (357/648)"- the numbers being their age in maturity hours compared to adult age


(You can speed the growth of an adolescent up using magical pies (skip them 144 hours, 72 hour cooldown, meaning you can use a max of two on an adolescent to skip a total of 288 of the 432 hours))