Run [man]phpinfo/man, find all lines containing "ini" (either case) that refer to a file, and look (or have them look) in all those file for the timezonedb setting/extension.
Here's some sample output from a devel box:
Configuration File (php.ini) Path => /usr/local/etc
Loaded Configuration File => /usr/local/etc/php.ini
Scan this dir for additional .ini files => /usr/local/etc/php
Additional .ini files parsed => /usr/local/etc/php/extensions.ini
user_ini.cache_ttl => 300 => 300
user_ini.filename => .user.ini => .user.ini
init_command_executed_count => 0
init_command_failed_count => 0
com_init_db => 0
Classes => AppendIterator, ArrayIterator, ArrayObject, BadFunctionCallException, BadMethodCallException, CachingIterator, CallbackFilterIterator, DirectoryIterator, DomainException, EmptyIterator, FilesystemIterator, FilterIterator, GlobIterator, InfiniteIterator, InvalidArgumentException, IteratorIterator, LengthException, LimitIterator, LogicException, MultipleIterator, NoRewindIterator, OutOfBoundsException, OutOfRangeException, OverflowException, ParentIterator, RangeException, RecursiveArrayIterator, RecursiveCachingIterator, RecursiveCallbackFilterIterator, RecursiveDirectoryIterator, RecursiveFilterIterator, RecursiveIteratorIterator, RecursiveRegexIterator, RecursiveTreeIterator, RegexIterator, RuntimeException, SplDoublyLinkedList, SplFileInfo, SplFileObject, SplFixedArray, SplHeap, SplMinHeap, SplMaxHeap, SplObjectStorage, SplPriorityQueue, SplQueue, SplStack, SplTempFileObject, UnderflowException, UnexpectedValueException
So, if it was happening on this box, it would be likely they have the "timezonedb" module listed in both /usr/local/etc/php.ini and in /usr/local/etc/php/extensions.ini ...
HTH,