Jazetopher

Corrected entry: Unless there are no labor restrictions limiting how many days a week they could work, it would be impossible to get a star every day of the month.

Correction: Since the store itself is holding the contest, it would seem appropriate that they could allow it's employees who are participating to have their schedules revised. For example, instead of working 8 hours for five days in a week, they could let them work 6 hours for all 7 days of the week, in order to obtain stars. This makes sense, as the people competing would all have to work exactly the same schedule so that the contest would give everyone involved the same chance of winning.

Jazetopher