Functions to switch the ENV timezone to and from UTC for use with mkt…

…ime.

timezone.cpp

@@ -0,0 +1,35 @@
+#include "timezone.h"
+
+#include <string>
+
+std::string stored_env_tz;
+
+void store_env_tz() {
+    //check if TZ is set, store current value
+    if(stored_env_tz.empty()) {
+        char* current_tz_env = getenv("TZ");
+        if(current_tz_env != 0) {
+            stored_env_tz  = std::string("TZ=");
+            stored_env_tz += std::string(current_tz_env);
+        }
+    }
+}
+
+void set_utc_tz() {
+   //change TZ to UTC
+   putenv((char*)"TZ=UTC");
+   tzset();
+}
+
+void unset_utc_tz() {
+    if(!stored_env_tz.empty()) {
+        putenv((char*)stored_env_tz.c_str());
+    } else {
+#ifndef _WIN32
+        unsetenv("TZ");
+#else
+        putenv((char*)"TZ=");
+#endif
+    }
+    tzset();
+}

timezone.h

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+#ifndef CORE_TIMEZONE_H
+#define CORE_TIMEZONE_H
+
+extern "C" {
+    void store_env_tz();
+    void set_utc_tz();
+    void unset_utc_tz();
+};
+
+#endif