Comment 5 for bug 1202626

If you take a look at the clock app designs provided at http://design.canonical.com/2013/03/app-patterns-applied-clock-key-journeys/ for adding a city, you will notice that while we are in the clock tab, the user is able to press the edit button to add a city. When the edit button is pressed, a new page is shown with a search box to enter the city the user wants to search and add. Hence the use case for a pagestack within a tab. There is also a similar requirement for alarms and timer. If you want to create an alarm, a new page is shown with the new alarm options.