PHP5 and Timezone problem

Hi everyone, i'm having some problems with squirrelmail and php5 and  
the timezone, i live in venezuela and the timezone
has been changed from GMT -4:00 to GMT -4:30, the system is reporting  
the time and date correctly however the web server
show the time like GMT -4:00 instead of GMT -4:30, this only happens  
if i use php5, if i use php4 everything is ok, now is there
any easy solutions to this???? i know i can use php5 and php4 at the  
same time but i would like to use php5 only, so i don' t know
how to fix this, i'm not an experienced web programmer but i have some  
friends who could help me to do the changes you propose
to my problem

thanks in advance
Daniel

PD: sorry about my english but i speak spanish

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