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're counting workdays or weekends, there are 22 weekdays and 8 weekend days. If you include the end date of May 1, 2015 which is a Friday, then there would be 23 weekdays and 8 weekend days including both the starting Wednesday and the ending Friday. 30 days is equal to 4 weeks and 2 days. The total time span from 2015-04-01 to 2015-05-01 is 720 hours. This is equivalent to 43,200 minutes.