Calculate daily means from 5-minute interval data

Provide dummy data (e.g. 5-10 lines), say like the contents of a csv file,
and calculate by hand what you'd like to see in the plot. (And describe
what the plot would look like.)

Eric,

Mea culpa! I extracted a set of sample data and forgot to include it in the
message. Here it is:

date,time,cfs
2020-08-26,09:30,136000
2020-08-26,09:35,126000
2020-08-26,09:40,130000
2020-08-26,09:45,128000
2020-08-26,09:50,126000
2020-08-26,09:55,125000
2020-08-26,10:00,121000
2020-08-26,10:05,117000
2020-08-26,10:10,120000
...
2020-08-26,23:10,108000
2020-08-26,23:15,96200
2020-08-26,23:20,86700
2020-08-26,23:25,103000
2020-08-26,23:30,103000
2020-08-26,23:35,99500
2020-08-26,23:40,85200
2020-08-26,23:45,103000
2020-08-26,23:50,95800
2020-08-26,23:55,88200

Rich