From 0256dffa8a52ce55b7853f2e642ae4cbe3834b7f Mon Sep 17 00:00:00 2001
From: Kevin Peizner <kevin.peizner@gmail.com>
Date: Wed, 25 Oct 2023 17:03:33 -0700
Subject: [PATCH] Fix incorrect formatting in NSISO8601DateFormatter
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By default, the NSISO8601DateFormatter uses the
NSISO8601DateFormatWithInternetDateTime formatting:

https://github.com/gnustep/libs-base/blob/master/Headers/Foundation/NSISO8601DateFormatter.h#L57

This equates to these format options:
```
NSISO8601DateFormatWithYear |
NSISO8601DateFormatWithMonth |
NSISO8601DateFormatWithDay |
NSISO8601DateFormatWithDashSeparatorInDate |

NSISO8601DateFormatWithTime |
NSISO8601DateFormatWithColonSeparatorInTime |
NSISO8601DateFormatWithTimeZone |
NSISO8601DateFormatWithColonSeparatorInTimeZone
```

The last option (`NSISO8601DateFormatWithColonSeparatorInTimeZone`)
causes the formatter to append "ZZ:ZZ" to the formatting string. But ZZ
maps to a timezone like this: “-0800" according to the ICU
documentation:
https://unicode-org.github.io/icu/userguide/format_parse/datetime/#date-field-symbol-table

The full format string that GNUStep puts together with the above
options is:

"yyyy-MM-dd'T'HH:mm:ssZZ:ZZ"

As a result, "ZZ:ZZ" will always translate to something like:

“-0800:-0800”

"ZZ:ZZ" should be "ZZZZZ" which is would output the timezone offset
once with the `:` separator between hours and minutes.

"yyyy-MM-dd'T'HH:mm:ssZZZZZ" is also the same format string used in
Apple's implementation according to their documentation:
https://developer.apple.com/documentation/foundation/nsiso8601dateformatter/1643114-init
---
 Source/NSISO8601DateFormatter.m | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Source/NSISO8601DateFormatter.m b/Source/NSISO8601DateFormatter.m
index 6d51afec6f..5d711e92c7 100644
--- a/Source/NSISO8601DateFormatter.m
+++ b/Source/NSISO8601DateFormatter.m
@@ -122,7 +122,7 @@ - (NSString *) _buildFormatWithOptions
     {
       if (_formatOptions & NSISO8601DateFormatWithColonSeparatorInTimeZone)
         {
-          result = [result stringByAppendingString: @"ZZ:ZZ"];
+          result = [result stringByAppendingString: @"ZZZZZ"];
         }
       else
         {