Travel days = end time-start time+1, including start time and end time.

This is a math application problem in the third grade of primary school. The first thing to know is the number of days in each month. As the saying goes, January is big, February is flat, March is big, April is small, May is big, June is small, July and August are big, September is small, October is big, November is small and December is big. Big finger 3 1 day, little finger 30 days. April is 30 days, that is, 9 days for business trip in April and 6 days for business trip in May. Total 15 days. The departure and return dates are counted.