You may switch the time format for events & tasks in our web application by editing the settings in the calendar app:

• Go to calendars.
• Click on the little cog wheel in the lower left next to + New Event.
• Select the desired time format.
• Click Save.
• The calendar will be reloaded and displayed in the destined time format.

Additionally you may set the start of the week to suit your local standard.

You can read more about this feature here: http://blog.fruux.com/2014/12/22/calendar-settings/.