#35 TryStr2DateTime: support the UK format and basic ISO 8601 (yyyymmdd)

[Thomas Mueller]

TryStr2DateTime in u_dzDateUtils tries the Windows format, the German format and ISO 8601 with dashes. Two formats that TryStr2Date accepts are missing:

• The UK format dd/mm/yyyy: the step is in TryStr2DateTime, but commented out, and its doc comment says "not done yet".
• Basic ISO 8601 without dashes (yyyymmdd): TryIso2Date parses it by hand, because the RTL cannot, but TryIso2DateTime has no such code.

So TryStr2DateTime rejects '20261014', and on a machine whose Windows format is not the UK one it also rejects '14/10/2026'; TryStr2Date accepts both. Measured with Delphi 12, the global FormatSettings set to M/d/yyyy with / and to dd/mm/yyyy with . (on an en-GB machine the Windows step already accepts '14/10/2026').

Because of this, TryVar2DateTime in u_dzVariantUtils calls TryStr2Date as a fallback after TryStr2DateTime (see [bugs:#68]). Once TryStr2DateTime supports both formats, TryVar2DateTime could call TryStr2DateTime alone.

[Thomas Mueller]

Fixed in revision #2441