This  formula will only update when the worksheet is recalculated or when you reopen  the workbook. That’s usually not a problem since the date only changes once a day.  Also, you may have to format the cell to give you your desired date format.

This  formula gives you both the date and time in the same cell (i.e. 19-May-03  9:00pm), however, is less useful because the time in the cell won’t change
until your worksheet recalculates or when you reopen your workbook. If you just  want the cell to display the time only, you’ll have to change the number format  by selecting Format, Cells, Number, Time, (select a desired time  format), OK