Re: Season Picker Not Showing Up
@SillyLily015 
Are you playing on console or PC/Mac?
Do the other Seasons options like weather show in your game?
The option to choose a season is only available when starting a brand new save. 
Have you made any changes to your game such as adding Mods or custom content?
Console: Turn off and unplug your console. When you plug it back in it will sync to recognize your game content properly.
PC/Mac:
First thing to try is to go to the Origin launcher to check for updates.
Run a "repair" by right clicking on the game icon.
If that does not work here is what I recommend.
Go to Documents\Electronic Arts\The Sims 4
Rename The Sims 4 to The Sims 4.old to preserve your saves, tray, screenshots and mods folders/files.
Run Repair from Origin as described in the troubleshooting guide.
Start the game without adding anything back as a test.
The game will automatically create fresh versions of all the folders/files.
If the game works correctly you will need to test your mods /custom content (CC) to see which they are causing the problem.
When adding/testing/deleting mods and/or cc it is important to delete the localthumbcache.package and any other cache files.
Using the 50/50 method is suggested to speed up the process.
Please reply back if this works or if you need more help.
Instructions are in the link below:
Troubleshooting tips
https://answers.ea.com/t5/Technical-Issues-PC/READ-FIRST-Troubleshooting-your-Game/m-p/3621199