HomeKit automation

as far as I can see you can choose a time or sunrise and sunset but not sunrise and sunset + offset

so the last part should be pretty easy done but the first part would likely require you to set the time for sunset and then adjust it when / if sunset change time across the year depending on where in the world you are located

you can try to request they adding an offset option using their feedback channel

since homekit does not seem to have a channel of it's own you can use homepods

Feedback - HomePod - Apple

This is easily do-able I think:

1. Open Home app, go to "Automation" bottom right icon
2. Create a new automation by clicking the "+" in the upper right
3. Select "A Time of Day Occurs".
4. Select "Sunset" then hit the small circle "i" at the far right. This allows you to adjust the time relevant to the sunset. Select "1 hour after sunset" from the choices. Note, this screen is where you can select the days of the week you want the automation to happen. Default is everyday (orange circle), click on a day to deselect it (grey circle).
5. Hit next, then select the lights you want to go on at this time and what percentage of dim you want.
6. Hit next and test automation or click on "done".

That's it for turning them on. Follow similar procedure and make another separate automation to turn them off when you want. Automations are easily altered, added, and deleted.

Hope that helps.

I’ve not set up any automations for lights yet, to know.

I’d already installed a perfectly good light fixture outside, with dusk to dawn lighting. Goes on at sundown and off at sun up.

You would think there’s automations for this based on your location to know automatically the sunrise and sunset times.

This might help

https://9to5mac.com/2018/04/04/homekit-weekly-004/