Because the deadline runs from your notice date rather than a fixed calendar day, two homes reassessed in different months can have appeal windows that do not overlap at all, which is why checking your own paperwork matters more than checking what a neighbour, a forum post or a general search result claims the date to be.
Missing that window closes the door until the next assessment cycle, and the Board of Revision generally will not hear a late filing on its merits, so the safest habit is opening the notice the day it arrives rather than the week the tax bill itself is due.
If the number still looks wrong once you have checked the date, comparable Saskatoon sales are the evidence that actually moves an appeal. Get your hand-reviewed valuation from Joel Dyck.