Bug: quickfiler-date-time-format-missing-invariant-culture

[drmoisan]

• Work Mode: full-bug

Summary

Every date/time .ToString(...) call in QfcHomeController.Metrics.cs, EfcHomeController.Metrics.cs,
QfcItemController.ViewerSetup.cs, QfcCollectionController.cs, and EfcItemController.cs omits
CultureInfo.InvariantCulture, while the adjacent numeric fields in the same methods pass it
explicitly. The : character in a .NET custom format string is the TimeSeparator custom specifier,
not a literal colon, so it resolves to DateTimeFormatInfo.TimeSeparator for whichever culture is in
effect. Under a culture such as it-IT, TimeSeparator is . rather than :, so now.ToString("HH:mm")
can render 13.05 instead of 13:05 if the host machine's regional settings differ from the author's
assumption.

Environment

• OS/version: Windows 11, Outlook VSTO add-in host
• Python version: not applicable (C# / .NET Framework 4.8)
• Command/flags used: not applicable (static code review finding)
• Data source or fixture: the session-metrics CSV emitted by the QuickFiler and EFC metrics writers, and
  on-screen/exception summary strings built from SentDate

Steps to Reproduce

1. Set the Windows regional format (or thread CurrentCulture) to a locale whose
   DateTimeFormatInfo.TimeSeparator is not : (for example it-IT, whose separator is .).
2. Run a QuickFiler filing session or an EFC move session so the session-metrics CSV writer executes,
   or trigger a code path that builds a SentDate/SentTime display string.
3. Inspect the emitted CSV time column, or the on-screen/exception summary string.

Expected Behavior

Every date/time field emitted by these files renders with a fixed, invariant separator regardless of
the host machine's regional settings, matching the invariant-culture handling already applied to the
adjacent numeric fields in the same methods (per the existing comment at
EfcHomeController.Metrics.cs:101-103: "the metrics file is machine-read, so numeric fields are
rendered with the invariant culture rather than the operator's locale").

Actual Behavior

None of the date/time .ToString(...) calls in the affected files pass CultureInfo.InvariantCulture,
so the rendered separator character is culture-dependent. Confirmed sites:

• QuickFiler/Controllers/QfcHomeController.Metrics.cs: curDateText/dataLineBeg
  ("MM/dd/yyyy", "hh:mm"/"HH:mm" after issue Bug: quickfiler-session-metrics-twelve-hour-time-format #645's fix) at lines 48 and 127.
• QuickFiler/Controllers/EfcHomeController.Metrics.cs: curDateText, curTimeText
  ("MM/dd/yyyy", "hh:mm"/"HH:mm" after issue Bug: quickfiler-session-metrics-twelve-hour-time-format #645's fix) at line 95-96, and the SentDate
  field at lines 118-119 ("MM/dd/yyyy", "HH:mm:ss") - SentDate is the CSV field issue Bug: quickfiler-session-metrics-twelve-hour-time-format #645 cites
  as the target 24-hour convention, and it is itself uncultured.
• QuickFiler/Controllers/QfcItemController.ViewerSetup.cs:498 - SentDate.ToString("HH:mm") in a
  user-facing summary string.
• QuickFiler/Controllers/QfcCollectionController.cs:1294,2300 - SentDate.ToString("HH:mm") in
  controller/log summary strings.
• QuickFiler/Controllers/EfcItemController.cs:612 - SentDate.ToString("HH:mm"), exposed as the
  SentTime property.

The CSV-writer sites (QfcHomeController.Metrics.cs, EfcHomeController.Metrics.cs) carry the higher
severity, since a wrong separator corrupts a machine-read artifact in the same way the numeric fields
were already protected against (see the comment cited above); the UI-facing sites
(QfcItemController.ViewerSetup.cs, QfcCollectionController.cs, EfcItemController.cs) are lower
severity, cosmetic-only.

Logs / Screenshots

• Attached minimal logs or snippet
• Snippet: none of the .ToString("MM/dd/yyyy"), .ToString("hh:mm")/.ToString("HH:mm"), or
  .ToString("HH:mm:ss") calls at the sites listed above pass a CultureInfo argument; contrast with
  the durationText/durationMinutesText calls in the same two Metrics.cs files, which do
  (.ToString("##0", CultureInfo.InvariantCulture)).

Impact / Severity

• Blocker
• High
• Medium
• Low

Medium for the two CSV-writer files (a wrong time separator on a machine-read, write-only artifact is
the same defect class already fixed for the numeric fields); Low/cosmetic for the three UI-facing
ToString("HH:mm") call sites. Filed as a single Medium entry since the writer sites dominate.

Source

From: docs/features/potential/2026-09-02-quickfiler-date-time-format-missing-invariant-culture.md