Revert "common/time_zone: Simplify GetOsTimeZoneOffset()"

src/common/time_zone.cpp

@@ -3,9 +3,8 @@
 // Refer to the license.txt file included.
 
 #include <chrono>
-#include <ctime>
-
-#include <fmt/chrono.h>
+#include <iomanip>
+#include <sstream>
 
 #include "common/logging/log.h"
 #include "common/time_zone.h"
@@ -17,8 +16,13 @@ std::string GetDefaultTimeZone() {
 }
 
 static std::string GetOsTimeZoneOffset() {
-    // Get the current timezone offset, e.g. "-400", as a string
-    return fmt::format("%z", fmt::localtime(std::time(nullptr)));
+    const std::time_t t{std::time(nullptr)};
+    const std::tm tm{*std::localtime(&t)};
+
+    std::stringstream ss;
+    ss << std::put_time(&tm, "%z"); // Get the current timezone offset, e.g. "-400", as a string
+
+    return ss.str();
 }
 
 static int ConvertOsTimeZoneOffsetToInt(const std::string& timezone) {