The Eastern part of Ontario
(most of Ontario and all the major towns & cities) lie in the Eastern Time Zone, which is 5 hours behind
Greenwich Mean Time (GMT-5) and the Western part of Ontario, west of 90° W longitude, are in the
Central Time Zone, which is 6 hours behind Greenwich Mean time (GMT-6).
Does
Ontario observe Daylight Saving Time?
Like most provinces in Canada, Daylight Saving Time is observed in Ontario, where the time is shifted forward by 1 hour, resulting in a 4 hours (GMT-4) and 5 hours (GMT-5) difference behind GMT for the Eastern and Western part of Ontario respectively.
After the Summer months the time is shifted back by 1 hour resulting in the normal time difference behind GMT.