Sunrise / sunset adjusted over the seasons when offline permanently?

Short version: does home assistant’s ‘Sun angle below horizon’ work when offline permanently?

Background: my father in law (86) has a shed for his pigeon keeping hobby, that is quite far from his house (approx. 22 meters, and another that we’re thinking of 68 meters but that’s for later). If I’m not mistaken you can’t get a reliable signal there with Z-wave (let alone zigbee which should be worse given the higher frequency used). Therefore, I’d like to put a Pi there locally to slowly dim on lights in the morning, and slowly dim off in the evening. Commercial solutions for arranging that are quite expensive and I use HA a lot at home. Could I put that Pi locally in that shed so it’s close to the lights/dimmers, permanently offline? I would move it to the house (where there is internet) occasionally for updates only.
The big question: do the sun ‘up’ and ‘down’ events’ time change throughout the year when offline? This setup would not work is HA doesn’t calculate that internally but needs the internet for it.

Thank you in advance for a response or referral, I could not find the answer myself.

Erwin

I can’t speak for HA, but ESPHome doesn’t require an internet connection for sunrise/sunset etc.

You would require a time source however, an external RTC for instance.

Cheaper than using a Pi…

If you have an electric supply to power the lights could you not use some like a homeplug to provide a connection?

I’m pretty sure those value are calculated from date / latitude in HA as well.

Well, once the Pi is booted and got proper time from the Internet, it keeps it.
Normally, the Pi has also a mean to “guess” the time upon a reboot, based upon the last value, fake-hwclock.

https://manpages.debian.org/jessie/fake-hwclock/fake-hwclock.8.en.html

So yeah, I think it’s viable if the Pi is connected to the internet from time to time.

Yes: HA uses python package astral for calculations.

Fantastic response, and just the answer I was hoping for!
Thank you all very much!