The options for date display (dd/mm/yy for example) is controlled through Regional settings. However - you don't need to change your settings - assuming their settings are set correctly for their region - the date format will show appropriate for their regional settings.

As far as time zone - again - Project does not know about time zone. If I create a task starting at 8:00 EST and send it to someone in Pacific - it will stay at 8:00 am.

I hoe this helps.