Hey, Scott

What PHP version we're talking about? I presume PHP5...

You can try also using
bool date_default_timezone_set ( string $timezone_identifier )

Timezones list: PHP: List of timezones in the group America - Manual
Documentation on your issue: PHP: date_default_timezone_set - Manual

However, I'd suggest saving all date\time value in UTC & than add timezone offset before the output. This is better than to write to users from Japan that all times are UTC -6 or something like that.

Let me know how it goes