There's some non-trivial amount of plays that only were performed on one day, so setting the closing date in the UI to the opening date at the worst case ensures a logical time span (if the user forgets to set the closing date explicitly) and best case helps the user jump a few days, rather than months, forward in the calendar to specify the closing date.
duhaime
commented
5 years ago 
There's some non-trivial amount of plays that only were performed on one day, so setting the closing date in the UI to the opening date at the worst case ensures a logical time span (if the user forgets to set the closing date explicitly) and best case helps the user jump a few days, rather than months, forward in the calendar to specify the closing date.