Illustrating invalid and ambiguous dates in F#

Program.fs

open System
open System.Globalization

let dtos =
  let ts  = TimeSpan(2, 0, 0)
  [|
    // Nothing weird about this date
    DateTimeOffset(2022, 6, 22, 2, 30, 0, ts)
    // This time is invalid in CEST because clock is set ahead at this date
    DateTimeOffset(2022, 3, 27, 2, 30, 0, ts)
    // This time is ambiguous in CEST because clock is set back at this date
    DateTimeOffset(2022, 10, 30, 2, 30, 0, ts)
  |]

let cest = TimeZoneInfo.FindSystemTimeZoneById "Central European Standard Time"
for dto in dtos do
  let s = dto.ToString ("s", CultureInfo.InvariantCulture)
  if cest.IsInvalidTime dto.DateTime then
    printfn "%s is invalid datetime" s
  elif cest.IsAmbiguousTime dto then
    let tos = cest.GetAmbiguousTimeOffsets dto
    printfn "%s is ambiguous datetime (Possible offsets: %A)" s tos
  else
    printfn "%s is normal" s