When setting up seasons, you can set up years in advance if your seasons don't change from year to year.
Example: My summer season always starts on the 1'st of May and ends on the 30'th of August.
You would then set your seasons group a few years ahead in time.
In the second box on the screenshot you would use the seasons in there and choose the month and day when that season starts.
If you have a special season, over holidays or any events that are yearly where your property is you can set that up on the dates you want and then check the box 'Special Season'. That season will the overwrite the dates where it overlaps.