Once a start date is selected, can the end date be defaulted to the same day?

When creating a new event, it would be handy if the end date could be set to the start date once it has been selected. It would also be nice if the min- defaulted to something like 00 rather than -min for the end time.

Is it also possible to put a break after the comma so that the hour and minute drop down boxes are less likely to be rendered on different lines on fixed width displays?