diff --git a/absl/time/internal/cctz/src/time_zone_info.cc b/absl/time/internal/cctz/src/time_zone_info.cc
index 101e20c1bd9..992c203f8f6 100644
--- a/absl/time/internal/cctz/src/time_zone_info.cc
+++ b/absl/time/internal/cctz/src/time_zone_info.cc
@@ -434,11 +434,7 @@ std::unique_ptr<ZoneInfoSource> FileZoneInfoSource::Open(
   // Map the time-zone name to a path name.
   std::string path;
   if (pos == name.size() || name[pos] != '/') {
-#ifdef PRINCIPIA_TZDIR
-    const char* tzdir = PRINCIPIA_TZDIR;
-#else
     const char* tzdir = "/usr/share/zoneinfo";
-#endif
     char* tzdir_env = nullptr;
 #if defined(_MSC_VER)
     _dupenv_s(&tzdir_env, nullptr, "TZDIR");
diff --git a/absl/time/internal/cctz/src/time_zone_libc.cc b/absl/time/internal/cctz/src/time_zone_libc.cc
index 362da1ab58b..03c1c84088f 100644
--- a/absl/time/internal/cctz/src/time_zone_libc.cc
+++ b/absl/time/internal/cctz/src/time_zone_libc.cc
@@ -42,9 +42,10 @@ namespace {
 
 #if defined(_WIN32) || defined(_WIN64)
 // Uses the globals: '_timezone', '_dstbias' and '_tzname'.
+// NOTE(phl): Microsoft, being in Redmond, counts West and not East.
 auto tm_gmtoff(const std::tm& tm) -> decltype(_timezone + _dstbias) {
   const bool is_dst = tm.tm_isdst > 0;
-  return _timezone + (is_dst ? _dstbias : 0);
+  return -(_timezone + (is_dst ? _dstbias : 0));
 }
 auto tm_zone(const std::tm& tm) -> decltype(_tzname[0]) {
   const bool is_dst = tm.tm_isdst > 0;
diff --git a/absl/time/internal/cctz/src/time_zone_lookup.cc b/absl/time/internal/cctz/src/time_zone_lookup.cc
index d1078de433e..475f1fe797f 100644
--- a/absl/time/internal/cctz/src/time_zone_lookup.cc
+++ b/absl/time/internal/cctz/src/time_zone_lookup.cc
@@ -165,10 +165,17 @@ time_zone local_time_zone() {
   }
 #endif
 #if defined(_WIN32)
+// The time_zone_info.cc code is incapable of finding the time zones on Windows.
+// (It looks in /usr/share/zoneinfo...)  Since we only care about the local
+// time, fall back to the libc implementation.
+# ifdef PRINCIPIA
+  zone = "libc:localtime";
+# else
   std::string win32_tz = GetWindowsLocalTimeZone();
   if (!win32_tz.empty()) {
     zone = win32_tz.c_str();
   }
+# endif
 #endif
 
   // Allow ${TZ} to override to default zone.
diff --git a/msvc/abseil-cpp.props b/msvc/abseil-cpp.props
index 4cd2d2e76b3..aa819b0b531 100644
--- a/msvc/abseil-cpp.props
+++ b/msvc/abseil-cpp.props
@@ -69,10 +69,7 @@
       <LanguageStandard_C>stdc17</LanguageStandard_C>
       <LanguageStandard>stdcpplatest</LanguageStandard>
       <MultiProcessorCompilation>true</MultiProcessorCompilation>
-      <PreprocessorDefinitions>
-        PRINCIPIA;
-        PRINCIPIA_TZDIR=R"literal($(SolutionDir)\..\absl\time\internal\cctz\testdata\zoneinfo)literal"
-      </PreprocessorDefinitions>
+      <PreprocessorDefinitions>PRINCIPIA</PreprocessorDefinitions>
       <SDLCheck>true</SDLCheck>
       <TreatWarningAsError>true</TreatWarningAsError>
       <WarningLevel>Level3</WarningLevel>