The CPU time reported for any particular process by 'ps' of procps-2.0.6
rolls over to zero when that process has consumed 24 hours of CPU time.
'top' still reports the correct time consumed, however. This occured
with no options and with the -C <procname> option; no other option
combinations were tested. The reported behavior occurred on an Intel
hardware platform, and was not tested on other hardware.
Fixed in Debian last year
-- Fixed in Debian without sending me a patch... :-P
Fixed in procps-2.0.7, which is in our current RawHide release.