DN629369199

Subject: clock command: proposals - DN [1]

harvey.davies@dar.csiro.au - 31 May 2000 - comp.lang.tcl

 1. I propose a new subcommand "clock cpu" which would give CPU time used
    in seconds as defined by the standard C expression "clock()/CLK_TCK".

 2. ISO 8601 allows a time zone suffix such as "+08:00" (8 hours ahead of
    UTC), "-09:30" (9.5 hours behind UTC) and "Z" (UTC). Tcl currently
    allows "-0930" but not "+0930" or "-09:30" or "Z" (which can be
    specified as "-0000"). I propose allowing all such ISO time zone
    suffixes.

 3. It would be nice to have an easy way of producing ISO 8601 strings.
    I suggest a new subcommand as follows:
    clock iso <clockValue> ?<timeZone>?
    where <timeZone> defaults to the local zone.
    So command
    % clock iso 5 +10:00
    would produce
    1970-01-01T10:00:05+10:00

 4. The current version contains a list of time-zone names and rules for
    deciding when daylight saving starts and finishes in each zone.  It
    may be useful to support these for USA, but it is quite impractical
    to do it for the whole globe. The rules for daylight saving in
    my country (Australia) vary from state to state and from year to
    year. Why not just use the explicit numeric zones as in ISO 8601?

 5. The current version stores <clockValue> as an integer number of
    seconds from 1970-01-01T00:00Z. I would prefer a 64-bit float to
    allow fractions of a second.  Astronomers and other scientists often
    measure time in days from 1858-11-17T00:00Z and this is called a
    "modified Julian date" or MJN. Note that adoption of this system
    would give a resolution of about a microsecond this year (2000).
    I propose using this system.

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