You must follow a separate day and night cycle in Pokémon Sword and Shield. This only happens in the game's wilderness area. Towns and routes are usually daytime, unless this changes for storytelling reasons.
When you enter a city, its lighting may be different from that of other cities. For example, when you visit Turffield, it appears to be later in the day, just before the evening. But it still shines. You want to know more because some Pokémon evolve into something specific when you bring it back to the time of day.
Eevee, for example, evolves into Mentali if you are fed up with happiness and it happens in the middle of the day. If, however, you level up with the specific levels of happiness at night, you get a Noctali. You want to make sure that you are setting the level at the right time so that you can transform your desired Pokémon into whatever evolution form you want to use. The same goes for Pokémon that prefer to show off at night.
So while towns and routes stay tied to story items to change their lighting, the Wilderness relies on your Switch's internal clock. So if you want to go out and evolve a particular Pokemon at night, visit the Wild Zone and the same goes when you want to evolve a Pokemon during the day.
You have the option of manually entering and changing your switch clock to change the wild area cycle to better suit your needs. You can stand in the middle of the wild area and freely adjust these settings. To make sure all Pokémon that show up at a particular time of day show up, go to a location and come back to reset spawns.
