type t = { created: Ptime.t option; edited: Ptime.t option }
let compare = compare
let rfc_string date = match date with Some t -> Ptime.to_rfc3339 t | None -> ""
let of_string (rfc : string) = match Ptime.of_rfc3339 rfc with Ok (t,_,_) -> Some t | Error _ -> None
let listing date = if Option.is_some date.edited then date.edited else date.created
let pretty_date = function
  | Some t -> Ptime.to_date t |> fun (y, m, d) -> Printf.sprintf "%04d-%02d-%02d" y m d
  | None -> ""