Why does HPUX login age passwords on a friday instead of a thursday
when using the unix password database password ageing (pw_age)?

The first day of the week is Thursday for password ageing based on week
no since 1-Jan-1970 so why does the HPUX login not prompt for password
change until 00:00 on Friday?

Example:

I change my password on Thursday Nov 3rd at 12 midday.

Time Now..: 1131019205 Thu Nov 3 12:00:05 2005
Today.....: 13090
Week No...: 1870
Week Start: 13090
Week Start: 1130976000 Thu Nov 3 00:00:00 2005
Next Week : 1131580800 Thu Nov 10 00:00:00 2005

My password age is set to 1 week, when should I expect to have to
change my password again? Thursday Nov 10th at midnight surely
(Beginning of Week No 1871):

Time Now..: 1131624003 Thu Nov 10 12:00:03 2005
Today.....: 13097
Week No...: 1871
Week Start: 13097
Week Start: 1131580800 Thu Nov 10 00:00:00 2005
Next Week : 1132185600 Thu Nov 17 00:00:00 2005

But HPUX11 does not prompt me for a new password until 00:00 on Friday
Nov 11th.

Another example:
Password changed Nov 7, again set to age 1 week, HPUX11 lets me in on
Nov 10th (thursday, start of next week) and prompts to change password
on Friday 11th.

Is this a bug in HPUX?
or perhaps my mis-interpretation of the password aging algorithm (in
which case, in what way? what is the correct algorithm)
or is my math just screwed?

Thanks