Graph number of concurrent events over time given start and end times

[Excel__lent]

Hello,

I have x number of sessions occurring noted by start times in column A and end times in column B in the format of "mm/dd/yyyy hh:mm".
Here is a sample of the data sorted by oldest time in column A first:

8/31/2015 22:01 8/31/2015 22:24
8/31/2015 22:01 8/31/2015 22:27
8/31/2015 22:01 8/31/2015 22:27
8/31/2015 22:01 8/31/2015 22:04
8/31/2015 22:01 8/31/2015 22:05
8/31/2015 22:02 8/31/2015 22:04
8/31/2015 22:02 8/31/2015 22:04
8/31/2015 22:02 8/31/2015 22:30
8/31/2015 22:02 8/31/2015 22:30
8/31/2015 22:02 8/31/2015 22:06
8/31/2015 22:08 8/31/2015 22:11
8/31/2015 22:10 8/31/2015 22:46
8/31/2015 22:18 8/31/2015 22:54
8/31/2015 22:28 8/31/2015 23:03
8/31/2015 22:29 8/31/2015 22:58
8/31/2015 22:30 8/31/2015 22:58
8/31/2015 22:32 8/31/2015 22:36
8/31/2015 22:33 8/31/2015 22:37
8/31/2015 22:40 8/31/2015 23:16
8/31/2015 23:03 8/31/2015 23:34
8/31/2015 23:06 8/31/2015 23:10
8/31/2015 23:13 8/31/2015 23:38
8/31/2015 23:13 8/31/2015 23:45
8/31/2015 23:42 9/1/2015 0:12
8/31/2015 23:42 9/1/2015 0:13
8/31/2015 23:44 9/1/2015 0:16
8/31/2015 23:55 9/1/2015 0:30
9/1/2015 0:14 9/1/2015 0:42
9/1/2015 0:15 9/1/2015 0:45
9/1/2015 0:20 9/1/2015 0:23
9/1/2015 0:27 9/1/2015 0:31
9/1/2015 0:34 9/1/2015 0:38
9/1/2015 0:42 9/1/2015 1:16
9/1/2015 0:47 9/1/2015 0:51
9/1/2015 0:53 9/1/2015 1:30
9/1/2015 1:05 9/1/2015 1:38
9/1/2015 1:21 9/1/2015 1:26
9/1/2015 1:33 9/1/2015 2:11
9/1/2015 1:37 9/1/2015 2:12
9/1/2015 1:42 9/1/2015 2:12

I need to create a line graph showing the number of concurrent sessions over time. I have seen many different ways to calculate concurrent sessions during each session listed, however, I can not figure out how to show how many concurrent sessions exist at a particular point in time; granularity down to the minute would be preferred.

In the above data set, I would expect to see 10 concurrent sessions at peak. I would like to graph the change in concurrent sessions with the number of sessions on the y-axis, and an interval of time on the x axis. For the example above, the x axis should show 22:00-03:00. Note that spanning past midnight into the next day is needed.

 

[oldbrewer]

8/31/2015 22:01 8/31/2015 22:24
8/31/2015 22:01 8/31/2015 22:27
8/31/2015 22:01 8/31/2015 22:27
8/31/2015 22:01 8/31/2015 22:04
8/31/2015 22:01 8/31/2015 22:05
8/31/2015 22:02 8/31/2015 22:04
8/31/2015 22:02 8/31/2015 22:04
8/31/2015 22:02 8/31/2015 22:30
8/31/2015 22:02 8/31/2015 22:30 X
8/31/2015 22:02 8/31/2015 22:06
8/31/2015 22:08 8/31/2015 22:11
8/31/2015 22:10 8/31/2015 22:46 X
8/31/2015 22:18 8/31/2015 22:54
8/31/2015 22:28 8/31/2015 23:03
8/31/2015 22:29 8/31/2015 22:58
8/31/2015 22:30 8/31/2015 22:58
8/31/2015 22:32 8/31/2015 22:36
8/31/2015 22:33 8/31/2015 22:37
8/31/2015 22:40 8/31/2015 23:16

do you count the two I marked X as concurrent ?

 

[Excel__lent]

8/31/2015 22:01 8/31/2015 22:24
8/31/2015 22:01 8/31/2015 22:27
8/31/2015 22:01 8/31/2015 22:27
8/31/2015 22:01 8/31/2015 22:04
8/31/2015 22:01 8/31/2015 22:05
8/31/2015 22:02 8/31/2015 22:04
8/31/2015 22:02 8/31/2015 22:04
8/31/2015 22:02 8/31/2015 22:30
8/31/2015 22:02 8/31/2015 22:30 X
8/31/2015 22:02 8/31/2015 22:06
8/31/2015 22:08 8/31/2015 22:11
8/31/2015 22:10 8/31/2015 22:46 X
8/31/2015 22:18 8/31/2015 22:54
8/31/2015 22:28 8/31/2015 23:03
8/31/2015 22:29 8/31/2015 22:58
8/31/2015 22:30 8/31/2015 22:58
8/31/2015 22:32 8/31/2015 22:36
8/31/2015 22:33 8/31/2015 22:37
8/31/2015 22:40 8/31/2015 23:16

do you count the two I marked X as concurrent ?

The short answer is yes.

The first pair marked with an "X" is from 22:02 - 22:30 and the second from 22:10 - 22:46. This means that from 22:10 - 22:30, these two are concurrently active.

The graph I am trying to achieve would have a y-axis value of n at 22:09, then n+1 at 22:10 when the second starts, and then n again at 22:30 when the first session ends (if you disregard all other influence on n outside of these two sessions).