nixpkgs/pkgs/development/libraries/qt-5/5.9/qtbase/tzdir.patch

Index: qtbase-opensource-src-5.9.0/src/corelib/tools/qtimezoneprivate_tz.cpp
===================================================================
--- qtbase-opensource-src-5.9.0.orig/src/corelib/tools/qtimezoneprivate_tz.cpp
+++ qtbase-opensource-src-5.9.0/src/corelib/tools/qtimezoneprivate_tz.cpp
@@ -70,7 +70,11 @@ typedef QHash<QByteArray, QTzTimeZone> Q
 // 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");
 
@@ -643,12 +647,16 @@ void QTzTimeZonePrivate::init(const QByt
         if (!tzif.open(QIODevice::ReadOnly))
             return;
     } else {
-        // Open named tz, try modern path first, if fails try legacy path
-        tzif.setFileName(QLatin1String("/usr/share/zoneinfo/") + 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(QLatin1String("/usr/lib/zoneinfo/") + QString::fromLocal8Bit(ianaId));
-            if (!tzif.open(QIODevice::ReadOnly))
-                return;
+            // Open named tz, try modern path first, if fails try legacy path
+            tzif.setFileName(QLatin1String("/usr/share/zoneinfo/") + QString::fromLocal8Bit(ianaId));
+            if (!tzif.open(QIODevice::ReadOnly)) {
+                tzif.setFileName(QLatin1String("/usr/lib/zoneinfo/") + QString::fromLocal8Bit(ianaId));
+                if (!tzif.open(QIODevice::ReadOnly))
+                    return;
+            }
         }
     }