From 8f9e25e81660d0627d2f7b340da3fb278193526c Mon Sep 17 00:00:00 2001
From: Alberto Spelta <albertospelta@users.noreply.github.com>
Date: Tue, 14 Jul 2026 13:42:37 +0200
Subject: [PATCH] Fix date format string to ignore per-user Windows regional
 overrides

BaseDateTemplate.GetDefaultFormatString built the default DateTime formatString via new CultureInfo(isoCulture).DateTimeFormat.ShortDatePattern. That constructor defaults to useUserOverride: true, so on a machine where the Windows user has customized Control Panel > Region short-date format (even under a plain "en-US" locale), the emitted formatString silently changes with it - e.g. "yyyy-mm-dd" instead of the culture-defined "m/d/yyyy".  This made generated templates non-reproducible across machines and was the actual cause of the StandardConfig_OfflineApply_MatchesSnapshot and CalendarStandardConfig_MatchesSnapshot golden-file failures. Pass useUserOverride: false so the format string depends only on the configured culture, not on the building machine's personal preferences.
---
 src/Dax.Template/Tables/Dates/BaseDateTemplate.cs | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/Dax.Template/Tables/Dates/BaseDateTemplate.cs b/src/Dax.Template/Tables/Dates/BaseDateTemplate.cs
index f81e500..226c5f2 100644
--- a/src/Dax.Template/Tables/Dates/BaseDateTemplate.cs
+++ b/src/Dax.Template/Tables/Dates/BaseDateTemplate.cs
@@ -27,8 +27,11 @@ public BaseDateTemplate(T config, CustomTemplateDefinition template, Predicate<C
     protected override string? GetDefaultFormatString(Dax.Template.Model.Column column, Microsoft.AnalysisServices.Tabular.Model model)
     {
         string isoCulture = string.IsNullOrWhiteSpace(IsoFormat) ? model.Culture : IsoFormat;
+        // useUserOverride: false - a template must produce the same DAX/TOM output regardless of the
+        // machine's personal Windows regional-format overrides (Control Panel > Region), which
+        // `new CultureInfo(name)` otherwise applies by default even for a fully-qualified culture name.
         return (column.DataType == DataType.DateTime)
-            ? new CultureInfo(isoCulture).DateTimeFormat.ShortDatePattern.Replace('M', 'm')
+            ? new CultureInfo(isoCulture, useUserOverride: false).DateTimeFormat.ShortDatePattern.Replace('M', 'm')
             : null;
     }