You can commit crime right after you get your PCC issued from your current country of residence as well. According to that logic all your PCC would have to be issued on the day of your AOR - which is mission impossible in the real world for most of the applicants.
When it comes to your most recent activities, that is what BG checks and security checks are for.
What is clear, is the requirement on PCC:
If you need a police certificate from a country or territory and:
•are currently living there, or received the police certificate before leaving, the police certificate must be issued within six months before you apply.
•have lived there in the past, the police certificate must be issued after you last lived in that country or territory.
http://www.cic.gc.ca/english/information/security/police-cert/intro.asp
So from above mentioned - less than six months old PCC is ok.
And for those older, it has to be issued after last time you visited that country.