HP-UX 'logins' command displays user account info. the -x option doesn't explain the last field reported:
PS 100506 7 175 -1
the last field is the number of days before the password expires to start warning the user. see the warn option of passwd(1) man page and passwd(4). The warn flag only works on trusted systems, so you'll see a -1 for non-trusted systems.
Remember that the system (at least on non-trusted boxes) will round to the nearest week, Thursday to be specific. So the report of when the passwd was last changed is not the actual day it happened, unless it happened to fall on a Thursday.