For services that use a roster, the first and last activity is usually signing in/out of a shift. Once you're logged in, right swipe to open the menu bar and tap 'Roster' to bring up the calendar view:
The days with a dot underneath them have events, such as shifts. Tap on the preferred day and the shift you wish to start or stop. The shift will show your start and end times and your assigned Room.
Clicking 'Start Shift' or 'End Shift' is all you need to do. The 'Working Hours' timer will track your time; if you need to leave comments, i.e. the reason for starting late or ending early, simply type them in the comment box and click 'Save'.