COUNTIF time interval falls between set of time ranges

Hi Everyone,

In one spreadsheet, I have a list of classes with the day(s) they occur along with their start and end times. See below. btw, M = Monday, T = Tuesday, W = Wednesday, R = Thursday, F = Friday

Course Days Start Time End Time
NU450 MT 7:00 AM 1:00 PM

NU266 M 6:00 AM 9:00 AM

NU615 WF 4:00 PM 7:00 PM

NU455 R 10:00 AM 12:00 PM

NU 220 WR 10:00 AM 2:00 PM

In another spreadsheet, I have a table that looks like this:
(Sorry about the format. Basically, each day has its own column and each time has its own row.)

6:00 AM M T W R F
6:30 AM
7:00 AM
7:30 AM
8:00 AM
8:30 AM
9:00 AM
9:30 AM
10:00 AM
10:30 AM
11:00 AM
11:30 AM
12:00 PM
12:30 PM
1:00 PM
1:30 PM
2:00 PM
2:30 PM
3:00 PM
3:30 PM
4:00 PM
4:30 PM
5:00 PM
5:30 PM
6:00 PM
6:30 PM
7:00 PM
7:30 PM
8:00 PM
8:30 PM
9:00 PM
9:30 PM
10:00 PM
10:30 PM
11:00 PM
11:30 PM
12:00 AM

I want to know, how many classes occur every half hour throughout the day. For example, how many classes occur from 6:00am - 6:29 am, 6:30 am - 6:59 am, etc. So if a class occurs from 7:00 am - 1:00 pm, it would be counted 12 times (1 for every half hour starting at 7:00 am and ending at 12:59 pm.

Eventually, I would like to put this on a line graph that has the times on the x axis and the # classrooms on the y axis.

I've been stumped on this forever. I would be more than ecstatic if someone could help me solve this problem.

Thanks thanks thanks!

Emily

Hello and welcome to the forum can you upload a sample book with expected results.