PlaceholderAPI is a plugin that allows server owners to easily display information from certain plugins anywhere they want. RealisticSeasons adds so-called placeholders using PlaceHolderAPI that can be used to display season, date, time, etc anywhere you want. It can be used in scoreboards, tab, bossbars, chat messages and more.
RealisticSeasons adds 2 types of placeholders, world-specific placeholders and player based placeholders. An example of a world specific placeholder is
%rs_season_spawn%. This placeholder will be replaced with the season of the world named "spawn". It doesn't matter what world the player is in, it will always display the information of the world "spawn". You can replace the "spawn" part with the name of your world. Another type of placeholder is the player based placeholder, for example,
%rs_season%. These placeholders use the world the player is currently in. It is less safe since it will not work in worlds like the nether or end. You should mostly stick to the world specific placeholders. All placeholders have a player based and world based variant, except for the temperature, which is player based only.