i managed to get this working. i had to take the j9-tzdata.jar file from a Cisco CUCM server and uploaded it to my freepbx tftpboot folder and added the below text to the phones xml file for it to start showing the correct time.
<tzdata>
<tzolsonversion>2017b</tzolsonversion>
<tzupdater>j9-tzdata.jar</tzupdater>
</tzdata>
<olsonTimeZone>Africa/Harare</olsonTimeZone>