https://www8.garmin.com/manuals/webhelp/fenix66s6xpro/EN-US/...
Or check the Solaris watch face which shows civil twilight, nautical twilight, astronomical twilight, and night.
https://apps.garmin.com/en-US/apps/0e019a96-aeb3-4aaf-81ed-4...
Above subject to which device you have.