Connect to your Pi to get to the command line. Then, open the Raspberry Pi configuration tool, better known as raspi-config, with the following command:

sudo raspi-config
Open "Localisation Options"

With Localisation Options open you'll be able to choose Change Timezone and select your local timezone.

From the command line, you can simply type date and confirm the date is displayed in your desired timezone.

pi@raspberrypi:~ $ date
Wed 28 Nov 11:10:33 PST 2018