CIRCADIAN RHYTHMS EVOLVED BEFORE STANDARD TIME BECAME A THING.

We'll close out our Daylight Saving Time posts with an elaboration on that claim.

While dark mornings are inevitable in winter, turning the clocks back gives us an extra hour of natural light. At least 15 minutes' exposure to natural daylight, as early as possible in the day, is crucial for good sleep and for falling asleep faster at night.

Why? Because natural light plays a big role in regulating circadian rhythm (your internal body clock), signalling when to be alert and when to sleep. Natural light suppresses melatonin (the sleepy hormone) to help you feel more alert in the day. But when the evening arrives and natural light fades, your circadian rhythm starts to increase melatonin production again. Your sleep drive (hunger to sleep) will therefore be at its highest come bedtime, helping you to fall asleep faster.

So winding the clocks back an hour gives you a chance to get more natural daylight exposure straight after waking and before getting on with the rest of your day. If the clocks didn't go back, you'd be travelling to work in the dark and coming home in the dark, which would make it much harder for your circadian rhythm to regulate as it should.

Working to the clock is a few seconds ago in an evolutionary hour.  If you're hunting, gathering, or farming, and you awake with the sun and nod off after dark, what matters is more alert time when there is work to be done, which is to say from spring planting to fall harvest, and more rest time when you're stretching out the food you've put up for winter.  Factories with time-clocks, and railroads with time-tables, and all the rest are still novelties.  It's easier, though, to adjust the clocks, sort of, to our circadian rhythms than it would be to have summer and winter business hours.

Turning the clocks back an hour during autumn provides more sunlight in the morning, whereas pushing them forward in spring brings lighter evenings.

Theoretically, mornings should get lighter when the clocks go back as the purpose of this time change is to gain an extra hour of light in the morning. This extra morning light is noticeable for a good few weeks. However, as sunrise gets so much later during winter months, light soon ends up coming later than it does in the summer despite the clocks changing.

Ultimately there is no way to avoid dark mornings and evenings in winter, but the clocks going back do give an extra hour of light in the morning to make cold commutes somewhat easier. Without the clocks going back, we wouldn't see the sun until around 9am in the winter.

Our agrarian ancestors would simply sleep in, unless they had cows to milk.  Fifty years ago, Our Political Masters went to year-round daylight saving time as a way to keep the evening commute in daylight, but that proved hazardous to the kiddos off to school in the morning.  Clocks proved easier to adjust than school schedules, and after a while spring ahead, fall back returned, although daylight saving time has crept earlier into spring and later into fall.  (Wisconsin, once upon a time, went off daylight saving time the final Sunday morning of September.  Made for interesting railroad timetables with Illinois staying on until the final Sunday morning of October.)

Those first hints of daylight, however, serve as a clue to your metabolism.

Getting sunlight exposure as early as possible in the morning boosts our cortisol levels. Cortisol is the stress hormone responsible for waking us up faster and making us feel alert. Therefore, spikes in the morning give us energy and alertness to power us through our daily tasks.

That outcome used to be natural, and nobody would make a fuss about slug-a-beds when the wake-up call was sunrise, rather than a church bell or your clock radio.  "Morning light is crucial to allow us to initiate sleep early enough in the evening, and wake early enough in the morning (preferably naturally without an alarm clock) for work and school starts."  And getting daylight during daylight hours helps calibrate one's internal clock.

We should aim for as much natural light as possible during the day as it can improve both sleep quality and morning alertness, making you feel more awake and prepared for the day.

Natural light is especially important in the morning, so I recommend sitting by a window when eating your breakfast or stepping outside to drink your morning coffee. That said, natural light exposure is beneficial throughout the day too. A walk in nature is a great way of combating the winter blues and promoting good sleep.

Plus it's not all about light exposure, fresh air can also help you sleep better.

Perhaps a few minutes of outdoor recess, morning and afternoon, ought to be something businesses and factories consider, and schools consider reviving.