Date and Time in RT-11 and RSX-11

From: Jerome Fine <>
Date: Sun Mar 21 12:52:41 1999

I am looking for a very simple explanation as to how the date and time
are handled in RSX-11? Just a short description which is parallel
to what is here about RT-11.

In RT-11, the date and time are two very separate quantities. There
is no interaction between the two except:

(a) When the user requests the time, the size of the time value is
      checked to see if it exceeds "24 hours"

(b) If the time exceeds "24 hours", the time is reduced by "24 hours"
      and the date is incremented by ONE day, the algorithm dependent
      on if the SYSGEN has rollover for end of month (and after 31-Dec-99)
      included or not.

The DATE command accepts dates from 01-Jan-73, although the date
of 01-Jan-72 is displayed correctly in the DIR utility. For non-Y2K
versions of RT-11 (V5.6 and prior), the DATE command accepts
and displays dates up to 31-Dec-99. For Y2K versions of RT-11
(V5.7), the DATE command accepts and displays dates up to

The DATE value is kept in a location within the resident monitor and
may be requested by any program via a .DATE request. The USR
tags a newly created file with the current DATE value (whatever
quantity is in the DATE value - no checking is done), otherwise,
the DATE is not used or manipulated by the operating system
(except as noted in b above) and the DATE command. Other
than the utilities (DIR, PIP, etc.) which look at the DATE and
especially look at the creation date of a file (which is not actually
looking at the actual date - but the DATE value at the time when
the file was created), RT-11 does not care about or use the DATE
in any manner and the operating system is totally independent of
the quantity in the DATE value and unaffected by that quantity.
I guess that changing the creation date of a file via PIP to be
the current DATE value via the SET option in PIP is an exception,
but no different than what happens when the USR creates a files
and uses the current DATE value as the creation date.

There could be application programs set up by the user which
do more than simply display or set the DATE value. DATIME.SAV
only does what the DATE command does, but a program executing
as a system job could do much more. In general, I want to ignore
such possibilities in both RT-11 and RSX-11.

One other very minor aspect. In RT-11, the LTC is used to increment
the time at either 50 or 60 Hertz. The time value is available to the
user in ticks. An RT-11 program can request certain time based
operations in terms of the number of ticks. Does RSX-11 have
similar types of things available?

Sincerely yours,

Jerome Fine
RT-11/TSX-PLUS User/Addict
Received on Sun Mar 21 1999 - 12:52:41 GMT

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