Both weather and time of day play an important role in Arceus. This Pokemon Legends Arceus Weather & Time Symbols Guide breaks down the symbols and icons both for what time of day it is and the current weather system on the region you’re in. Unfortunately, there’s no trick to changing weather and time quickly or easily in Pokemon Legends Arceus.
If you want it to be a different time of day you need to either rest at a camp or at your hut in the village. If you want a specific weather condition, you simply need to rest at a camp until you get the weather condition you want. Make sure, when you rest, to always rest until a certain time. Just resting for a little while will only heal your Pokemon and will not move time forward much at all.