How do I get today's date?

I'm trying to add a display on my game that shows the number of shopping days until Christmas. How can I get the current date in a format that can be compared to another date?

I found this plugin

https://rexrainbow.github.io/C3RexDoc/plugins.md/site/rex_date/index.html

but I don't understand how to use it. If somebody could give me an ELI5-level walkthrough on how it works I'd be your best friend.