You can manipulate the start time and end time by using special keyboard shortcuts. Using these shortcuts, you can do the following:
Shift by unit
Shifting date or time by unit allows you to change the opposite date/time element to the one selected by the corresponding date or time component. For example, if you shift by unit the month time element in the start time, the month time element in the end time increments by one month exactly, including days, minutes, and seconds. This also works for months that have different end days.
To shift by unit:
Fit to unit
Fitting date or time to unit allows you to synchronize the selected time element to the zero position of that time element in the start time and end time. For example, an Operator clicks on the hh time element of the Start picker, which shows 19:30:05.123. After Ctrl + click, the Start hour time element shows 19:00:00.000, and the End time element shows 20:00:00.000. Now the time span represents exactly one hour, synchronized on the hour.
To fit to unit: