I do not have date_default_timezone_set(timezone); anywhere in my site . I am using time() and date() at lot of places in my code. Will it create problems because i have not set default timezone?
It's recommended to set in php.ini:
date.timezone = "America/Los_Angeles"
Or in your PHP script:
date_default_timezone_set('America/Los_Angeles');
If you don't do this, PHP will warn you. But your date() time() functions will continue to work with OS datetime settings.
It depends on PHP version but starts from PHP 5.4 UTC timezone will used if it didn't set. But it highly recommended set timezone. http://www.php.net/archive/2011.php#id2011-09-27-1 Also, php will throw E_WARNING message if timezone isn't valid or empty