From d9ee2187011ab1328bf7161e7a751325c4a41208 Mon Sep 17 00:00:00 2001
From: Timothy Flynn <trflynn89@pm.me>
Date: Tue, 25 Jan 2022 15:46:49 -0500
Subject: [PATCH] LibCore: Support DateTime string formatting of the form %z

This formats the time zone offset as "+hhmm" or "-hhmm".
---
 Userland/Libraries/LibCore/DateTime.cpp | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/Userland/Libraries/LibCore/DateTime.cpp b/Userland/Libraries/LibCore/DateTime.cpp
index cc433e0aba9..1d0bfa0c409 100644
--- a/Userland/Libraries/LibCore/DateTime.cpp
+++ b/Userland/Libraries/LibCore/DateTime.cpp
@@ -105,6 +105,23 @@ String DateTime::to_string(const String& format) const
     StringBuilder builder;
     const int format_len = format.length();
 
+    auto format_time_zone_offset = [&]() {
+        auto offset_seconds = -timezone;
+        StringView offset_sign;
+
+        if (offset_seconds >= 0) {
+            offset_sign = "+"sv;
+        } else {
+            offset_sign = "-"sv;
+            offset_seconds *= -1;
+        }
+
+        auto offset_hours = offset_seconds / 3600;
+        auto offset_minutes = (offset_seconds % 3600) / 60;
+
+        builder.appendff("{}{:02}{:02}", offset_sign, offset_hours, offset_minutes);
+    };
+
     for (int i = 0; i < format_len; ++i) {
         if (format[i] != '%') {
             builder.append(format[i]);
@@ -217,6 +234,9 @@ String DateTime::to_string(const String& format) const
             case 'Y':
                 builder.appendff("{}", tm.tm_year + 1900);
                 break;
+            case 'z':
+                format_time_zone_offset();
+                break;
             case '%':
                 builder.append('%');
                 break;