Strange.
Your query worked for me (with a different nodename), although I had to add
the date to restrict the output to the last 7 hours:

tsm: SSDADSM>select date_time, message from actlog where nodename='PRATHW1'
and
time(actlog.date_time) >= current_time - 7 hours and date(actlog.date_time)=
current_date

If you do:  q actlog search=VTCAT.CC.VT.EDU  begintime=now-7

Do you get anything back?  Should be the same records in both cases...