Feedback:

1. You should mention TOML in your first paragraph. "Why not TOML" exists at the end

2. how often are "instants"/dates really specified? Are you baking this in for TOML parity?

If you want leaner, drop this. If nothing else it's a lot of grammar.

If you want to lean in to "A value's type comes from its syntax", I'd suggest taking a cue from postgres and JS -- extensible literals. With JS tagged literals it would look like date`2026-09-19T14:00:00Z`. Conforming readers can fall back.

I'd use ver`3.1.0` 1000x more in config files than dates... I do like durations being baked in though.

Solid improvements over TOML and YAML.