Current:
It is common to type a desired frame number into either the start time, end time, or current time fields, then click away to do something else, and then press a hotkey only to discover that the time field still had focus and your desired time value has now been replaced.
Desired:
Clicking anywhere outside of the time fields should remove focus and any subsequent key presses will not apply to that field until it is given focus again by clicking on it again.