I would suggest cross-tabs report, but I am not sure how to ensure that all columns are present.
you could create this using variables, but it won't be pretty.
you could probably also do it using running totals if you like them more.
for the variables, you would need as many as the hours you are tracking (so 24 ifyou are tracking a complete day)
1)in the group header you would set them all to 0
2)then in your detail section, you increment the correct variable for the time of day
3)in the group footer you would display each variable in the column desired.
HTH