The challenge I will be taking this year is to implement each day in a separate language, 25 languages in total.
The languages are:
1. Fortran 90
2. Perl 6
3. SWI-Prolog
4. OCaml
5. Julia
6. C (Clang)
7. PHP 7.2
8. F# (Mono & Ionide-fsharp)
9. C++ (Clang C++14)
10. Rust
11. Swift 5
12. Clojure
13. Java 13
14. Crystal
15. C# (Mono)
16. Python 3.7
17. Scala
18. Javascript (NodeJS 12.9.1)
19. Groovy 2.5.8 (JVM 9.0.1)
20. Typescript 3.7.3 (TSNode 8.5.4, NodeJS 12.9.1)
21. Kotlin (kotlinc-jvm 1.3.60, JRE 9.0.1)
22. Go 1.13.4
23. Ruby 2.6
24. Elixir 1.8.2 (Erlang/OTP 22)
25. Haskell