[Riesling]

Sorry for being imprecise, but I actually meant Standard Time (as in noon at about 12pm). Our circadian rhythms are not as flexible as many people think. There are many studies showing that people sleep less if the sun sets later, causing a net sleep loss with related health problems.

[tbabb]

> if the sun sets later

The sun sets when it sets. We are choosing what clock label to put on that moment.

Getting up an hour earlier and thinking of the same clock position as "later in the day" is exactly the same as using DST— except clock noon and solar noon won't be permanently misaligned.

[taeric]

You know solar noon is not necessarily noon. Right? Pretty sure it changes throughout the year, too. If so, that seems more an argument for dst. I'll check in a bit. Someone may just know, though.

[kgwgk]

Solar noon changes a bit through the year, but the range is just half an hour: https://www.sundials.co.uk/eot

[taeric]

Odd, this would seem to be a data point for DST being just half an hour.

That said, that chart is suspicious for not having jumps for DST. How does that work?

[kgwgk]

DST doesn’t have anything to do with the oscillation of the true noon at any location by +/-15 minutes around the year (that cycle is not even summer/winter).

[taeric]

How? Noon literally shifted by an hour per last night. So there should be a jump in the chart. Not a smooth line. A jump.

[kgwgk]

The chart shows at what time noon happens when you have a 24-hour clock calibrated to get it right on average. For example, a clock showing GMT assuming you’re in Greenwich.

If you add or subtract hours to your clock instead of keeping a 24 hours day length then yes, you will have jumps. But those jumps are caused by you playing with the clock, they are not real.

The fact that Daylight Savings Time exists doesn’t have anything to do that the duration of the day is sometimes a few seconds longer and sometimes a few seconds shorter than 24 hours.

If noon was always 24 hours after the previous one the line in that chart would be flat. With discontinuities if you want to include DST shifts in the chart, but I really don’t see the interest in doing so.

The rationale for applying DST has nothing to do with that variation, it would be just the same if the time from noon to noon was always 24 hours.