Yahoo Mail has a feature for changing the display language and time zone information. Click on the Options link and select Mail Options from the available menu list.
Click on the Account Information link available on the left hand side.
This will prompt to verify your password again. Enter the password and click on the Sign In button. In the Yahoo account info page, scroll down to the Account Settings section and click on the Set language, site and time zone link.
In the Set Language, site and time zone page, using the Regional Site and Language and Time Zone dropdown you can change the display language and set the Time Zone for Your Yahoo Mail Account. After selecting the preferred values click on the Save button to apply the changes.