http://www.cic.gc.ca/english/infORmation/security/police-cert/intro.asp
In general, you and all the people in your family who are 18 or older need to get a police certificate. You must get one from each country or territory where you have lived for six or more months in a row since the age of 18. (For example, if you lived in a country for eight months but left on a two-week vacation, that counts as living there for eight months.)
For the country you currently live in, the police certificate must be issued no more than six months before you apply.
For countries where you have lived for six months or more, the police certificate must be issued after the last time you lived in that country.
If your certificate is in a language other than English or French, send it when you apply, along with the original copy of a translation done by a certified translator.