What I do is put this line in my .htaccess file: (it should be in your web site's root directory, or you may have to create it)
SetEnv TZ America/Montreal
That way it applies site-wide, and you don't have to change individual scripts.
Note that if you are using MySQL, it will always be in the Pacific time zone, and there's nothing you can do about it (until they upgrade to MySQL 4.1, which supports time zones.) You'll have to manually add/subtract the appropriate number of hours whenever you use time functions such as NOW().
You can use the "tzselect" command to figure out what the correct time zone for you is.