I found this on the CIC website:
if you visited, worked or lived in a country for two months, left for a few years, then returned for four months, that counts as spending six months there. In this case, you would need a certificate.
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.
So my parents have been living here since last September, and they need one from Canada. They last lived in China before 2014, so they only need a record that's issued after they came to live in Canada.
Is my understanding of this statement correct?