[itsm] How do I set the calendar timezone for India?

Hi, I’m using OTRS at a UK company, where we have an offshore support team in India. For their queue, I’m trying to create a calendar appropriate to their business hours; however OTRS will not let me set their timezone to UTC +5:30 as the drop-down list only contains hourly intervals. How do we create calendars for countries whose timezones are not a simple multiple of hours from GMT/UTC? Regards, Richard Cross.