From 9605be19bb41f89ec23706cfb8ea14773f49351b Mon Sep 17 00:00:00 2001
From: Timothy Flynn <trflynn89@pm.me>
Date: Tue, 25 Jan 2022 16:04:54 -0500
Subject: [PATCH] LibCore: Support DateTime string formatting of the form %:z

This formats the time zone offset as "+hh:mm" or "-hh:mm". This doesn't
appear to be strictly POSIX, but it is how Linux implements this format.
---
 Userland/Libraries/LibCore/DateTime.cpp | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/Userland/Libraries/LibCore/DateTime.cpp b/Userland/Libraries/LibCore/DateTime.cpp
index 1d0bfa0c40..490a27d2f6 100644
--- a/Userland/Libraries/LibCore/DateTime.cpp
+++ b/Userland/Libraries/LibCore/DateTime.cpp
@@ -105,7 +105,7 @@ String DateTime::to_string(const String& format) const
     StringBuilder builder;
     const int format_len = format.length();
 
-    auto format_time_zone_offset = [&]() {
+    auto format_time_zone_offset = [&](bool with_separator) {
         auto offset_seconds = -timezone;
         StringView offset_sign;
 
@@ -118,8 +118,9 @@ String DateTime::to_string(const String& format) const
 
         auto offset_hours = offset_seconds / 3600;
         auto offset_minutes = (offset_seconds % 3600) / 60;
+        auto separator = with_separator ? ":"sv : ""sv;
 
-        builder.appendff("{}{:02}{:02}", offset_sign, offset_hours, offset_minutes);
+        builder.appendff("{}{:02}{}{:02}", offset_sign, offset_hours, separator, offset_minutes);
     };
 
     for (int i = 0; i < format_len; ++i) {
@@ -235,7 +236,15 @@ String DateTime::to_string(const String& format) const
                 builder.appendff("{}", tm.tm_year + 1900);
                 break;
             case 'z':
-                format_time_zone_offset();
+                format_time_zone_offset(false);
+                break;
+            case ':':
+                if (++i == format_len)
+                    return String::empty();
+                if (format[i] != 'z')
+                    return String::empty();
+
+                format_time_zone_offset(true);
                 break;
             case '%':
                 builder.append('%');