in reply to Older people should know their age on Mercury

I was able to make this work with Date::Calc. Like so: 
#!/usr/bin/perl -w
#mercury.pl-how old am I in Mercury Years.
use Time::localtime qw(localtime);#also for ctime
use POSIX;                          #for floor
use Date::Calc qw(Delta_Days);

#length of Mercury year in earth days
$mercuryRevolution = 87.97;

#get birthday stats for Oct 1, 1977 
$birthDay = 1;$birthMonth=9;$birthYear=1977;

$daysAlive = Delta_Days($birthYear,$birthMonth,$birthDay,
                        localtime->year()+1900,localtime->mon(),
                        localtime->mday());
$mercuryYears = POSIX::floor($daysAlive / $mercuryRevolution);

$nextMercuryBday = $daysAlive % $mercuryRevolution;
$nextBirthDate =  ctime(time()+ ($nextMercuryBday *24*60*60));
#strip hours,minutes,seconds from ctime string
$nextBirthDate =~ s/(\w+\s\w+\s\d+)(\s\S+\s)(\w*)/$1,$3/;

print "\nYou are ".$mercuryYears." Mercurian Years old",
      "\nYour next Mercurian Birthday is in " . $nextMercuryBday . 
      " days\n", "on ". $nextBirthDate;

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It's a shorter program and it would even work for Dracula, now.

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Re: Re: Older people should know their age on Mercury
by ehdonhon (Curate) on Oct 03, 2001 at 05:40 UTC
    Yes, that is a better way of doing it, except that Date::Calc is 1-based in it's months instead of 0-based, So if you wanted to find out for a person born in October, you would need to set $birthMonth to 10.

    I find that to be an annoying feature of Date::Calc. That and the way it sets up the days of the week as (1..7) = (Monday .. Sunday). The pod sites all sorts of ISO specs that say this is the way it should be. Unfortunately, localtime and timelocal don't agree. This means an enormous opportunity for off-by-one errors if you need to switch back and forth.
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      This 0..11 rang for months is a wart inherited from C. I am amazed it is still there in Perl 5. Same thing for year 101 instead of 2001. Fortunately, most modules have correct ideas about date elements. Fortunately too, there is RFC 48 for Perl 6, that will fix the warts.
[reply]
      You are correct. It seemed to work until I put in 0 for a January date. That's an invalid argument for the Delta_Days function. which means I also have to add one to localtime->mon() as well. Cause the Time::localtime module starts it's indices at zero. Quite Inconsistent. Thanks.
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