nixpkgs/pkgs/development/libraries/qt-6/patches/qtbase-tzdir.patch

diff --git a/src/corelib/time/qtimezoneprivate_tz.cpp b/src/corelib/time/qtimezoneprivate_tz.cpp
index 627a4a81..a5f50acc 100644
--- a/src/corelib/time/qtimezoneprivate_tz.cpp
+++ b/src/corelib/time/qtimezoneprivate_tz.cpp
@@ -51,7 +51,11 @@ typedef QHash<QByteArray, QTzTimeZone> QTzTimeZoneHash;
 // Parse zone.tab table, assume lists all installed zones, if not will need to read directories
 static QTzTimeZoneHash loadTzTimeZones()
 {
-    QString path = QStringLiteral("/usr/share/zoneinfo/zone.tab");
+    // Try TZDIR first, in case we're running on NixOS.
+    QString path = QFile::decodeName(qgetenv("TZDIR")) + QStringLiteral("/zone.tab");
+    // Fallback to traditional paths in case we are not on NixOS.
+    if (!QFile::exists(path))
+        path = QStringLiteral("/usr/share/zoneinfo/zone.tab");
     if (!QFile::exists(path))
         path = QStringLiteral("/usr/lib/zoneinfo/zone.tab");
 
@@ -727,18 +731,21 @@ QTzTimeZoneCacheEntry QTzTimeZoneCache::findEntry(const QByteArray &ianaId)
         if (!tzif.open(QIODevice::ReadOnly))
             return ret;
     } else {
-        // Open named tz, try modern path first, if fails try legacy path
-        tzif.setFileName("/usr/share/zoneinfo/"_L1 + QString::fromLocal8Bit(ianaId));
+        // Try TZDIR first, in case we're running on NixOS
+        tzif.setFileName(QFile::decodeName(qgetenv("TZDIR")) + QStringLiteral("/") + QString::fromLocal8Bit(ianaId));
         if (!tzif.open(QIODevice::ReadOnly)) {
-            tzif.setFileName("/usr/lib/zoneinfo/"_L1 + QString::fromLocal8Bit(ianaId));
+            tzif.setFileName(QLatin1String("/usr/share/zoneinfo/") + QString::fromLocal8Bit(ianaId));
             if (!tzif.open(QIODevice::ReadOnly)) {
-                // ianaId may be a POSIX rule, taken from $TZ or /etc/TZ
-                auto check = validatePosixRule(ianaId);
-                if (check.isValid) {
-                    ret.m_hasDst = check.hasDst;
-                    ret.m_posixRule = ianaId;
+                tzif.setFileName("/usr/lib/zoneinfo/"_L1 + QString::fromLocal8Bit(ianaId));
+                if (!tzif.open(QIODevice::ReadOnly)) {
+                    // ianaId may be a POSIX rule, taken from $TZ or /etc/TZ
+                    auto check = validatePosixRule(ianaId);
+                    if (check.isValid) {
+                        ret.m_hasDst = check.hasDst;
+                        ret.m_posixRule = ianaId;
+                    }
+                    return ret;
                 }
-                return ret;
             }
         }
     }