by date field using sum-counts
e.g. for January 1995:
period 1995-01-01-00:03:06 1995-01-31-23:59:59
fields scheme value total-accesses total-bytes fbr-accesses fbr-bytes \
fbr-email-accesses fbr-email-bytes fbr-howftp-accesses fbr-howftp-byte\
s ftp-accesses ftp-bytes gopher-accesses gopher-bytes http-accesses ht\
tp-bytes mserv-accesses mserv-bytes
data per_hour 00 33041 667544892 25 389373 (11) (1997660) (2) (30529) \
6224 25296 4297 1149 12332844 25636 399145858 7 2712520
data per_hour 01 24671 723051021 34 427543 (16) (1335244) (2) (312348)\
5224 3657
...