daylight saving time (DST) — also known as summer time or daylight time — to standard time kicked in on Sunday. Daylight saving time 2021: Here’s when to turn your clocks back and how it started The bi-annual flip — clocks are set an hour forward in March — has become a controversial topic, with several provinces wanting to do away with the century-old practice.The idea behind DST is to conserve energy and make better use of daylight during spring and summer when the days are longer.Because the change leads to a mismatch between the local clock and our body’s internal clock, it can have measurable impacts on health, including sleep loss and heart problems, experts say.“We shouldn’t be putting ourselves through this twice a year,” said.