From bug-octave-request at bevo dot che dot wisc dot edu  Sun Dec  3 22:41:45 2000
Subject: possible error in time, ctime and related routines
From: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
To: Gerard van Dijnsen <g dot vandijnsen at chello dot nl>
Cc: bug-octave at bevo dot che dot wisc dot edu
Date: Sun, 3 Dec 2000 22:41:28 -0600

On  3-Dec-2000, Gerard van Dijnsen <g dot vandijnsen at chello dot nl> wrote:

| I believe the output of time and ctime and related routines might be
| offset by one hour. I am not too sure of myself, because the same bug
| seems to exist in my linux distribution's date command. Perhaps I am
| one who is entirely wrong here... If that is the case, sorry.

As Trond says, I think you are confused by local time vs. UTC.  The
epoch is defined as 00:00:00 GMT 1 Jan 1970.

| I have added one of my own functions here. I have not extensively tested
| it,
| but it seems to work ok. It converts dates in the format produced by the
| clock function to seconds after the epoch. I believe it works ok, though
| it
| seems to be one hour off compared to octave (and the linux date
| command), which
| is how I found the bug (if it is one). Anyways, feel free to use the
| code if
| you find it useful! The function name sucks, so please think of somthing
| more appropriate :-)

The number of seconds since the epoch is given by the time function.
It is a built-in function, so it will be much faster than your
clck2sec function, and it will also not depend on the local time zone.
And, I think you really do want the number of seconds since the
epoch to be independent of the local time zone.

Since Octave's clock function is just:

  function retval = clock ()

    tm = localtime (time ());

    retval = zeros (1, 6);

    retval(1) = tm.year + 1900;
    retval(2) = tm.mon + 1;
    retval(3) = tm.mday;
    retval(4) = tm.hour;
    retval(5) = tm.min;
    retval(6) = tm.sec + tm.usec / 1e6;

  endfunction

your function undoes everything except the time zone conversion
that happens in the call to localtime.

BTW, Octave doesn't have mod function (it has rem instead).  Does
Matlab have mod now?  If so, how is it different from rem?

jwe



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