Your kneecap (patella) sits over the front of your knee joint. As you bend or straighten your knee, the underside of the patella glides over the bones that make up the knee. Strong tendons help attach the kneecap to the bones and muscles that surround the knee.
NETWORKDAYS.INTL(D3,E3,0000000) calculates whole days between the two dates (no weekends, no holidays). NETWORKDAYS(D3,E3,0000000,$A$16:$A$24) calculates whole working days days between the two dates (Sat/Sun weekends, holidays as per your list in $A$16:$A$24). Difference in non-working days between the two dates.
If you want to calculate the number of days between two dates you can simply subtract the older date from the newer date. The result will be an integer that represent the days between dates. In the example, the formula in cell D6 returns 365, since there are 365 days between 1/1/1999 and 1/1/2000. Dates in Excel are simply serial numbers that start on 1/1/1900. In the example, the formula in cell D6 simply subtracts the numeric value of 1/1/1999 (36161) from the numeric value of 1/1/2000 (36526) to get a result of 365.