Assessment notices are typically mailed in the spring, and the appeal window that follows is short, which is why reading the notice the day it arrives, rather than filing it away, is worth doing even if nothing looks obviously wrong at first glance.
Missing the printed deadline generally means waiting for the next reassessment cycle, since the Saskatchewan Assessment Management Agency does not usually accept a late challenge outside the window the City of Saskatoon sets for that year's notices, and the taxable share stays fixed at 80 percent of assessed value in the meantime.
If your assessment looks out of line with what similar homes have actually sold for, checking that against real market data before the deadline is the productive use of the time you have. Get your hand-reviewed valuation from Joel Dyck.