10 facts about the fall season

In admiration of fall's splendour, John Donne once wrote, "No spring nor summer beauty hath such grace, as I have seen in one autumnal face."

Tell that to your friends bemoaning the end of patio season.

But you don't have to be an English poet to appreciate the season's bright colours and bountiful harvest, which help smooth the transition to shorter days and colder nights.

Canadians never step into the season at the same time — some wear shorts in September as others pile on sweaters — but the autumnal equinox on Friday marked the official start of fall in the Northern Hemisphere, making this the first weekend of fall.

In case you don't know much about the September equinox and the season between sandals and skis, here are some facts to share by the fire:

• The September equinox in 2011 — which marks the first day of autumn in the Northern Hemisphere and first day of spring in the Southern Hemisphere — occurred at 5:04 a.m. ET on Friday.
• The fall equinox usually happens around mid-September, typically on Sept. 22 and surrounding days. Equinoxes usually occur six hours later each year, but jump back a day during a leap year. Six months of darkness begin at the North Pole while six months of light begin at the South Pole.
• The word equinox comes from the Latin words for "equal" and "night." Understandably then, many think there are equal hours of daylight and night at the equinox. This isn't quite correct. Daylight on the equinox is actually several minutes longer than the night. The days when there are 12 hours of day and 12 hours of night, called the equiluxes, are a few days closer to winter than the equinoxes and fall on different dates at different latitudes.
• Jupiter is expected to glide bright across the sky this weekend, a treat that should last until Halloween.
• The French Republican Calendar — used in France for 12 years in the late 18th and early 19th centuries, before Napoleon Bonaparte abolished it — used the autumn equinox as New Year's Day. The first day of the month was called Vendémiaire, or "wine harvest."
• In Japan, both the spring and autumn equinox are national holidays.
• In neopaganism, the spring and autumn equinoxes are called Ostara and Mabon, respectively, although these names are modern in origin and don't correspond to any ancient festivals.
• Leaves change colour because they need a break, a winter of rest, after a summer of photosynthesizing (using sunlight to convert water and carbon dioxide into sugar). Sick trees often change colour and shed too early, which means they don't have long to live, according to arborist Jim McCready.
• Pigments are responsible for the distinct colours of the leaves in the fall: chlorophyll for green; carotenoid for yellow, orange and brown; anthocyanins for red. As sunlight decreases, the tree stops producing chlorophyll and the carotenoid in the leaves shows through with yellows, oranges and soft browns.
•  Daylight time will have most Canadians setting their clocks back an hour (or "falling back") on Nov. 6. Most of Saskatchewan, parts of Quebec and pockets of Ontario and British Columbia do not follow daylight time.