Outlook Web App allows users to change the time zone using the Options. From Office 365 home screen, click the Option link available under the Outlook section.
In the Options screen, click the Settings link available on the left hand side navigation pane.
The settings section would then display the following list of option, click regional from the list.
Under Regional Settings, navigate to to Current time zone section. Using the Current time zone drop down one can change the time zone in Outlook Web App. After selecting the preferred time zone from the drop down list, click Save link to confirm and apply the changes.