Brew stopped working

On my system Brew has now stopped working…

I get this error when running a command: /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require’: incompatible library version - /Users/krist/.gem/ruby/2.6.0/gems/date-3.0.1/lib/date_core.bundle (LoadError)

System is MacOSX 10.15.5

What could have caused this, and how do I fix this? Preferably whithout having to throw out all my gems.

Are you using your mac for ruby development?