In Salesforce the date-time values stores in (UTC) Coordinated Universal Time and according to the Time Zone adjusts them to display to the users Time zone offset.
Whenever one of the value is returned in Salesforce it will automatically adjust for the time zone specified by the organization preferences.
To change the time zone follow the steps:
Click on the Username that is located on the above of the tab bar, a menu popups here click on
“My Settings” options.
Next, click on “Personal” and select “Language & Time Zone”, Language & Time Zone view will display.
Here you will see some fields like:
1. Time Zone: here select your primary time zone.
2. Local: select your country or geographic region.
3. Language: select your primary language. All text and online help appear in the language you select.
4. Email Encoding: select the character set and encoding option for email that you send from Salesforce.
And after modifying fields click on “Save” button.