Yes, steaky is correct.
You can count the days outside of Canada in certain circumstances as days that satisfy the residency requirement: You can count each day you accompanied a Canadian citizen outside Canada provided that the person you accompanied is your spouse or common-law partner (or other qualifying relation). If you are accompanying a permanent resident, there is an additional requirement that the PR you are accompanying must be employed by a Canadian company or be in public service for the country to count towards residency.
As far as documenting days for PR renewal, is it necessary to account for every little trip/vacation or just days where you actually took up residence outside the country? If it's every little trip I need to instigate some sort of tracking mechanism. I will never remember it all 5 years from now!