∀ {leap : Bool} (ordinal : Std.Time.Day.Ordinal.OfYear leap) (idx : Std.Time.Month.Ordinal) (acc : ℤ)
  (h : ↑ordinal > acc) (h₁ : ↑ordinal ≤ acc + ↑(Std.Time.Month.Ordinal.days leap idx)),
  1 ≤ ↑(Std.Time.Internal.Bounded.cast ⋯ ⋯ ((Std.Time.Internal.Bounded.LE.mk ↑ordinal ⋯).sub acc)) ∧
    ↑(Std.Time.Internal.Bounded.cast ⋯ ⋯ ((Std.Time.Internal.Bounded.LE.mk ↑ordinal ⋯).sub acc)) ≤ 31