Why no date and time?
 replies(1): 
Built in Rust, with bindings for Python and WebAssembly, as well as syntax highlighting in VSCode. I made it for those like me who hand-edit JSONs and want a breath of fresh air.
It's at a good enough point that I felt like sharing it, but there's still plenty I wanna work on! Namely, I want to add (real) Node support, make a proper LSP with auto-formatting, and get it out there before I start thinking about stabilization.
Making them part of the language would increase the complexity of parsers - how would you validate that a date is actually valid? It's doable (YAML and TOML do it, after all) but requires extra steps.