TOML has a datetime type (both with or without tz), as well as plain date and plain time:

  start_at = 2026-05-27T07:32:00Z  # RFC 3339
  start_at = 2026-05-27 07:32:00Z  # readable

We should extend it with durations:

  timeout = PT15S  # RFC 3339

And like for datetimes, we should have a readable variant:

  timeout = 15s   # can omit "P" and "T" if not ambiguous, can use lowercase specifiers

Edit: discussed in detail here: https://github.com/toml-lang/toml/issues/514