Vdom_time_ago.Formattype t = | Time_ago| Short_string_ago| Short_string_until| Custom of now:Core.Time_ns.t -> reference:Core.Time_ns.t -> stringTime_ago generates a user-friendly string representing the time difference (e.g. 1h 30s turns into "1 hour ago"), while Short_string_ago and Short_string_until are equivalent to Time_ns.Span.to_short_string