CNBC.com will default the data on the chart you are viewing to the time zone you are viewing from. So if you are viewing a quote page from California, your chart will show data in Pacific Standard Time. Likewise, if you are viewing a quote page from New York, you will see Eastern Standard Time.
To change the time zone you are viewing from, select the Settings (gear icon) above the chart on the quote page you are viewing. From the dropdown, scroll to down to LOCALE. Select "Change Timezone" and choose the timezone you want. Your chart will update automatically.