Question: how to subtract days and hours in excel?
Answer: In cell B2 type the start time, enter a space, and then type “a” for AM or “p” for PM, and press Enter. In cell C2, type the end time, including “a” or “p” as appropriate, and press Enter. ... 
In cell D2, subtract the end time from the start time by typing the formula: =C2-B2, and then pressing Enter.