If unix./ linux - bpps gives an indications:
root 763 1 0 Oct 29 ? 0:43 /usr/openv/netbackup/bin/private/nbatd -c /usr/openv/var/global/vxss/eab/data
root 770 1 0 Oct 29 ? 0:06 /usr/openv/netbackup/bin/bpcd -standalone
root 923 1 0 Oct 29 ? 0:00 /usr/openv/pdde/pdag/bin/mtstrmd
root 766 1 0 Oct 29 ? 0:04 /usr/openv/netbackup/bin/vnetd -standalone
root 786 1 0 Oct 29 ? 7:13 /usr/openv/netbackup/bin/nbdisco
root 926 1 0 Oct 29 ? 27:24 /usr/openv/netbackup/bin/nbemm
root 858 1 0 Oct 29 ? 11:54 /usr/openv/netbackup/bin/nbevtmgr
<snip>
Looking at processes that run all the time, eg. nbemm, bpdbm etc I see here that NBU restarted on my test system on Oct 29th.
If I restart NBU, we see that the system was restarted today (it shows time for today), then just the date the next day onwards.
root 15860 15845 0 15:05:15 ? 0:01 /usr/openv/netbackup/bin/nbproxy dblib nbpem
root 15971 15881 0 15:05:43 ? 0:07 /usr/openv/netbackup/bin/admincmd/bpstsinfo -DPSPROXY
root 15655 1 0 15:04:39 ? 0:02 /usr/openv/netbackup/bin/nbdisco
root 15793 1 0 15:04:50 ? 0:00 /usr/openv/pdde/pdag/bin/mtstrmd
root 15706 1 0 15:04:41 ? 0:05 /usr/openv/db//bin/NB_dbsrv @/usr/openv/var/global/server.conf @/usr/openv/var/
root 15798 1 0 15:04:52 ? 0:03 /usr/openv/netbackup/bin/nbemm
bpps in windows shows similar output