[flang-commits] [flang] [llvm] [flang-rt] Add implementation for date_and_time on Windows (PR #190174)

[Michael Kruse via flang-commits]

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@@ -376,14 +375,26 @@ GetGmtOffset(const TM &tm, fallback_implementation) {
   // return -HUGE to report that this information is not available.
   const auto negHuge{-std::numeric_limits<Fortran::runtime::CppTypeFor<
       Fortran::common::TypeCategory::Integer, KIND>>::max()};
-#ifdef _AIX
+#if defined _AIX
   bool err{false};
   auto diff{computeUTCDiff(tm, &err)};
   if (err) {
     return negHuge;
   } else {
     return diff;
   }
+#elif defined _WIN32
+  DYNAMIC_TIME_ZONE_INFORMATION tzi;
+  std::uint32_t tzid{GetDynamicTimeZoneInformation(&tzi)};
+  if (tzid == TIME_ZONE_ID_INVALID) {
+    return negHuge;
+  }
+
+  std::int32_t bias{tzi.Bias};
+  bias += (tzid == TIME_ZONE_ID_DAYLIGHT ? tzi.DaylightBias : tzi.StandardBias);
+
+  // Bias is minutes behind GMT, and we need minuetes ahead.
----------------
Meinersbur wrote:

```suggestion
  // Bias is minutes behind GMT, and we need minutes ahead.
```

https://github.com/llvm/llvm-project/pull/190174