Calendar icon date wrong on Launchpad

If the problem is still there, try booting into the Safe Mode using your normal account. Disconnect all peripherals except those needed for the test. Shut down the computer and then power it back up after waiting 10 seconds. Immediately after hearing the startup chime, hold down the shift key and continue to hold it until the gray Apple icon and a progress bar appear. The boot up is significantly slower than normal. This will reset some caches, forces a directory check, and disables all startup and login items, among other things. When you reboot normally, the initial reboot may be slower than normal.

Safe Mode - About El Capitan
also Sierra

Safe Mode Startup – El Capitan. also Sierra

See this article If the wrong date or time is displayed in some apps on your Mac - Apple Support

It may be a bug. You can send Apple feedback. Make sure you let them know you are using FInnish.

Feedback - macOS - Apple

They may not answer but at least they will be aware of the problem.

Also an update: occasionally, the date on Launchpad IS correct. Then again, it sometimes is displayed wrong. I think it is a some sort of bug.

It is not a bug , in my system correct dates are shown in calendar app both in launch pad and if calendar app is in the dock .

If the settings are altered difficulties will come to sign in iTunes , appleid.apple.com , www.icloud.com

For the time being create a new user account and observe it How to test an issue in another user account on your Mac - Apple Support

And I am not sure if you have altered any settings in your Mac if so the date will differ .

In your screen shots some unwanted apps are shown ? Did you use https://etrecheck.com/

Use it and remove those apps , read the report first try to clean by yourself if any difficulties come you can post the results here , members of the forum will read it and try to solve .

See some articles Set the date and time on your Mac - Apple Support

Date & Time preferences on Mac - Apple Support

In system preferences > date and time settings are altered like unchecking the box of set date and time automatically , changing the continent ( by clicking on drop down arrows ) , in time zone > if you uncheck the box of set time zone automatically using current location .Correct city and country must be shown .

And in security and privacy > click on privacy > if you uncheck enable location services .

If read and write permissions are changed for guest , shared , home folder these problem will occur .

You're welcome.