ELI5/Summer Solstice Sunset Time


It seems to me that the longest day of the year (summer solstice) sunset times have shifted.

In my memory, sunset used to occur closer to 10pm. (For reference, I’m in Missouri, USA, central time zone.) the latest sunset this year was about 8:55pm.

Does the sunset shift over time based on orbits or rotation? If so, can you give a brief overview of what has happened & the timeline of that?

Thank you!

In: 4

There may be some tiny change in solstice sunset times from year to year but I’d be surprised if it was more than a minute or two.

You might be remembering extra light due to dusk. It takes a while for it to get dark after the sun has gone below the horizon. For example, they generally don’t start July 4th fireworks until after 10.

Check websites that give numbers for “civil twilight”.

The sunset time will not differ to any significant degree for the same location compared to solar noon. But what time depends on where you are and the difference between solar time and the time zone you are in. So if you move east in the same time zone sunsets are earlier, they get later if you move west. The time in a timezone only matches the solar time in one latitude line, around it the time is before or after solar time,

Moving north/south has a significant effect on the time of the sunset. you get 24 hours of sune close enough to the poles. On the poles themself there is a single sunrise and sunset every year.

I have sunset at 00:04 today and sunrise at 01:02. So it is below the horizon for 1 hour. If that change by half an hour noon would be at 12:00 which means I would need to move 7.5 degrees west to be where they line up.

Sunsets are not when it gets dark, it is when the sun is not visible above the horizon. You have civil, nautical, and astronomical twilight If we look at Jefferson City https://www.timeanddate.com/sun/usa/jefferson-city the sun set today at 20:36, civil twilight is at 21:08, nautical at 21:28, and astronomical at 22:34 So civil twilight around 30 minutes after sunset, nautical 1 hours and astronomical 2 hours

Civil Twilight is approximately when it is enough light to do stuff outdoors. Nautical twilight is when the horizon is still visible so you could for example see a ship as a dark object in front of a brighter sky. Astronomical Twilight is when there is no light in the atmosphere that can disturb observation. They are today defined with the sun a number of degrees below the horizon, the angles were picked to match what I describe

If we assume you live in the same location as when you remember sunset at around 2200 we can use the Jefferson City differences as an approximation. If the sunset is at 20:55 the civil twilight is around 21:30, the nautical at 22:00, and the astronomical around 23:00 It looks to me that your memory is about when the horizon is still visible not when the sun is no longer above the horizon.

Try to go out and compare what you see to what you remember and afterward compare it to sunset and twilight time. If you have not moved the difference between sunset and twilight is like the explanation. If you have to move it can just be the change in the difference between solar and timezone time the sunset and twilight difference can still be in effect.