Daylight Saving Time in Ontario

2025 schedule

Ontario keeps EST in winter and shifts one hour forward for the summer.

Time until the next change

Current local time:

Economic Impact of DST in Ontario

The economic effects of Daylight Saving Time in Ontario are real but modest, and studies disagree on their size. Retailers and hospitality businesses generally favour DST, arguing that lighter evenings encourage shopping, dining out and other after-work spending — the US retail lobby was one of the main forces behind the 2005 extension of the DST period.

The transitions themselves carry a cost. Research from Chmura Economics has put the one-off economic cost of the spring change in the United States at roughly $430 million a year, driven by lost productivity, workplace injuries and the health effects of a disrupted night's sleep.

Health Considerations for Ontario Residents

The spring transition is the one that hurts. A study in Open Heart found the risk of heart attack rose by about 24% on the Monday after clocks went forward, before falling back to normal within the week. Research published in Current Biology found a 6% rise in fatal traffic accidents in the week following the spring change, with the effect strongest in the morning and in the western parts of time zones.

The autumn change, when most people gain an hour, shows no comparable spike. Researchers attribute the difference to sleep loss rather than to the clock change itself.

Does DST Actually Save Energy?

This was the original justification, and it is the claim that has held up worst. A US Department of Energy report to Congress in 2008 measured the four weeks added to DST in 2007 and found a saving of about 0.5% of daily national electricity use — real, but small.

Other work has found no saving at all. A well-known study of Indiana, which adopted DST statewide in 2006, found residential electricity use actually rose by 1–4%: households used less lighting but more air conditioning on hot summer evenings. Any lighting savings are also partly offset by extra petrol use as people travel more in the lighter evenings.

Technology and Time Changes in 2025

Phones, computers and anything else that syncs with an internet time server handle the transition on their own. What still catches people out in Ontario is the long tail of devices that don't: car dashboards, ovens and microwaves, wall clocks, older thermostats, and cheap alarm clocks with a DST setting hard-coded to a schedule that has since changed.

For anyone running servers, the transitions are a recurring source of bugs — duplicated or missing local timestamps around the changeover, cron jobs that fire twice or not at all, and stale operating system timezone databases. Storing timestamps in UTC and keeping the tzdata package current avoids almost all of it.

Getting ready

• Check and replace smoke detector batteries when changing clocks - it's a good reminder!
• Use the phrase 'Spring forward, fall back' to remember which direction to change your clocks.
• Remember that not all countries change on the same date - check international meeting times carefully.
• Set your clocks before going to bed to avoid confusion in the morning.