[ci skip] Added UPGRADING entry for GH-12413

Closes GH-12964.

Author: marc-mabe

UPGRADING

@@ -115,6 +115,10 @@ PHP 8.4 UPGRADE NOTES
 2. New Features
 ========================================
 
+- Date:
+  . Added static methods
+    DateTime[Immutable]::createFromTimestamp(int|float $timestamp): static.
+
 - DOM:
   . Added constant DOMNode::DOCUMENT_POSITION_DISCONNECTED.
   . Added constant DOMNode::DOCUMENT_POSITION_PRECEDING.

UPGRADING.INTERNALS

@@ -58,6 +58,9 @@ PHP 8.4 INTERNALS UPGRADE NOTES
 
  e. ext/date
    - Added the php_format_date_ex() API to format instances of php_date_obj.
+   - Added the php_date_initialize_from_ts_long() and
+     php_date_initialize_from_ts_double() to initialize a php_date_obj with
+     the given unix timestamp using GMT +00:00.
 
  d. ext/pcre
    - php_pcre_match_impl() now no longer has a use_flags argument.