How to Simply Calculate Worktime with Excel

There is an easy way to calculate worktime with Excel. See the below image. 

1) Cell B2 is the start time. Type in the time you want, for example "21:14." Press "Cmd" + ";" or "Shift" + "CTRL" + ";" to input the current time.
2) Cell C2 is the end time.
3) Use the below formula in cell D2:
      =HOUR(C2-B2)+(MINUTE(C2-B2)/60)
4) Add all the worktimes by using the below formula:
      =SUM(drag over the cells you want to add)

CF. For those who don't want to see the error sign on the Excel sheet, try the below formula:
=IF(C2,IF(HOUR(B2)+(MINUTE(B2)/60)<HOUR(C2)+(MINUTE(C2)/60), HOUR(C2-B2)+(MINUTE(C2-B2)/60), HOUR(C2)+24-HOUR(B2)+MINUTE(C2)/60-MINUTE(B2)/60),"")