Calculate weekdays in a month

[Pilly]

Hi,
can anyone finish this question posed in the url below.

Here

I want to work out how many weekdays there are in a month using the code on this link and for Jan 04, it gives 23 when i look at the wall planner its 22.

Can anyone tell me what is wrong with it?

[LordShryku]

http://www.phpbuilder.com/board/showthread.php?s=&threadid=10266712&highlight=week+days
Using sort of a makeshift of that, this would work:

function workingdays($month,$year) {
   if(is_numeric($month) && is_numeric($year)) { //need to be a numbers
      if($month > 12) {
         return false;
      }
      $start = mktime(0,0,0,$month,1,$year);
      $end   = ($month ==12) ? mktime(0,0,0,1,1,$year+1):
                               mktime(0,0,0,$month+1,1,$year);
      $bet   = ($end - $start)/86400;
      $days  = 0;
      for($i=0;$i<$bet;$i++) {
         $newday = date("w",($start + ($i*86400))); // increment day of week
         if($newday != 0 && $newday != 6) { // if not sat. or sun.
            $days++; // increment days
         }
      }
      return $days;
   }
   return false;
}

echo workingdays(1,2004);

[Shrike]

God damn this one has been bugging me all day. I'm not even sure if this works:

$date = "2004-02-01";
$daysinmonth = date("t", strtotime($date));
$modulus = $daysinmonth % 7;
$startday = date("D", strtotime($date));
$days = array( "Mon" => 01, "Tue" => 02, "Wed" => 03, "Thu" => 04, "Fri" => 05, "Sat" => 06, "Sun" => 07 );
if($modulus + $days[$startday] <= 6) $extra = $modulus;
if($modulus + $days[$startday] == 7) $extra = $modulus -1;
if($modulus + $days[$startday] > 7) $extra = 0;
echo "Total weekdays ".(20 + $extra);

Hmm mine goes a day out in May 2004. Bugger 🙂

[AstroTeg]

This was bugging me too... Here's my try. Appears to work well:

function daysinmonth($month, $year)
{
	$daysmonth = date('t', mktime(0,0,0,$month,1,$year));
	$day = date('w', mktime(0,0,0,$month,1,$year));
	$count = 0;
	for($a = 0; $a < $daysmonth; $a++)
	{
		if(($day + $a) % 7 > 0 && ($day + $a) % 7 < 6)
			$count++;
	}  // end for($a = 0; $a < $daysmonth; $a++)

return $count;
}  // end function daysinmonth($month, $year)

// // //

echo daysinmonth(1, 2004) . '<br>';
echo daysinmonth(2, 2004) . '<br>';
echo daysinmonth(3, 2004) . '<br>';
echo daysinmonth(4, 2004) . '<br>';
echo daysinmonth(5, 2004) . '<br>';

[Shrike]

Fixorised it:

$date = "2004-01-01";
$daysinmonth = date("t", strtotime($date));
$modulus = $daysinmonth % 7;
$startday = date("D", strtotime($date));
$total = 20;
for($i=0;$i<$modulus;$i++){
  $mod_day = date("D", (strtotime($date)+(86400*$i)));
  if($mod_day != "Sat" && $mod_day != "Sun"){
    ++$total;
  }
}
echo "For $date, $total weekdays.";

Blatantly stolen Shryku's day counting 🙂

[LordShryku]

Originally posted by Shrike
Blatantly stolen Shryku's day counting 🙂

Don't make me call the SCO lawyers and sue you for everything you got! Wait....SCO's going bankrupt....err....hrmmmm....yeah, go ahead and steal it. 😃

[Shrike]

Ha!

/me sells code to MikeRoweSoft

[LordShryku]

What a poor bastard that guy is. Wonder if I legally change my name to Bill Gates....can I get sued too?

[Weedpacket]

Mine's fastest 🙂.

Weedpacket's time: 0.095577001571655
LordShryku's time: 0.308596849441530
Shrike's time:     0.093461990356445
Astroteg's time:   0.156485080718990

By a twentieth of a second when checking every month from 1980 to 2030 inclusive!!!

Probably 'cos there's only one call to mktime, one to date, and no loops.

function weekdays_in_month($month, $year)
{
	$first = mktime(0,0,1,$month,1,$year);
	// The first day of the month is also the first day of the
	// remaining days after whole weeks are handled.
	list($first_day,$days) = explode(' ',date('w t',$first));
	$weeks = floor($days/7);
	$weekdays = $weeks*5;
	$remaining_days = $days-$weeks*7;

if($remaining_days==0)
	return $weekdays; // Only happens most Februarys

if($first_day==0)
{
	$weekdays += $remaining_days-1;
}
elseif($first_day==6)
{
	$weekdays += max($remaining_days-2,0);
}
else
{
	$weekdays += $remaining_days-1+
	             ($remaining_days<=(6-$first_day))-
                 ($remaining_days>(6-$first_day));
}

// Correction if last day of month is Saturday -
// but only if the first day of the month is not a Saturday as well
// (which only happens twice in the period 1970-2038)
// Wish I knew why this was necessary so's I could get rid of it.
if($first_day!=6 && ($first_day+$days-1)%7==6)
	$weekdays++;
return $weekdays;
}

Shrike: you wanna check, say, May, August and October 2004?

[Weedpacket]

Ah, that's why there are weird months; that first condition should be "starts on Sunday or ends on Saturday"...yes, that makes much more sense.

function weekdays_in_month($month, $year)
{
	$first = mktime(0,0,1,$month,1,$year);
	// The first day of the month is also the first day of the
	// remaining days after whole weeks are handled.
	list($first_day,$days) = explode(' ',date('w t',$first));
	$weeks = floor($days/7);
	$weekdays = $weeks*5;
	$remaining_days = $days-$weeks*7;

if($remaining_days==0)
	return $weekdays; // Only happens most Februarys

$weekdays += $remaining_days-1;
// Neither starts on Sunday nor ends on Saturday
if($first_day!=0 && ($first_day+$days-1)%7!=6)
{	// Adjust for weekend days.
	$weekdays += ($remaining_days<=(6-$first_day))-
                 ($remaining_days>(6-$first_day));
}


return $weekdays;
}

(Ps: Faster

Weedpacket's time: 0.096036911010742
LordShryku's time: 0.348363161087040
Shrike's time:     0.097055912017822
Astroteg's time:   0.161774873733520

)

[AstroTeg]

Hmm, I hadn't thought to combine the two mktime() calls into one. I know the for() I have is pretty expensive, but I'm kinda wondering what the drop in time would be like if 1 mktime() was issued instead of two.

function daysinmonth($month, $year)
{
    list($day, $daysmonth) = explode(' ', date('w t', mktime(0,0,0,$month,1,$year)));
    $count = 0;
    for($a = 0; $a < $daysmonth; $a++)
    {
        if(($day + $a) % 7 > 0 && ($day + $a) % 7 < 6)
            $count++;
    }  // end for($a = 0; $a < $daysmonth; $a++)

return $count;
}  // end function daysinmonth($month, $year) 

[Weedpacket]

Originally posted by AstroTeg
Hmm, I hadn't thought to combine the two mktime() calls into one. I know the for() I have is pretty expensive, but I'm kinda wondering what the drop in time would be like if 1 mktime() was issued instead of two.

In my tests a it typically saves about 50µs (again, over every month in the period 1970-2030), but fluctuations in server activity can wipe out something that small without any trouble (I'm measuring wall time, so the fluctuations show up in the tests).

Weedpacket's time: 0.099636077880859
LordShryku's time: 0.349784135818480
Shrike's time:     0.103041887283330
Astroteg's time:   0.167834043502810
Astroteg2's time:  0.167527914047240

[LordShryku]

What I don't see is a check for proper formatting. I threw the little is_numeric checks in there for that. Then again, I'm sure all of our codes could be made a bit better, and had I known this would become a competition, I would have spent more than a minute on it :p

[AstroTeg]

Very interesting. That for loop is much more expensive then I thought it was going to be...

[Weedpacket]

Originally posted by LordShryku
What I don't see is a check for proper formatting. I threw the little is_numeric checks in there for that.

Yah, but I generally separate the two tasks. When I was testing yours I took that bit out, 'cos I was sure I'd be passing it valid parameters. If I couldn't be sure I'd have called a separate function viz:

function workingdays($month,$year) {
	//need to be a numbers
   if(is_numeric($month) && is_numeric($year) && 0<$month && $month<=12)
	{ return workingdays_reckless($month, $year);
	}
	return false;
} 

[Shrike]

Give me your timer function and I will.

My code could be optimized alot I'm sure, for a start the two strtotime() calls could be just one by assigning the result of the first call 🙂

And mine has fewer lines! :p

[Weedpacket]

Originally posted by Shrike
Give me your timer function and I will.

Oh, just microtime() wrapped around

for($y=1980; $y<=2030; ++$y)
{	$shrike_weekdays[$y]=array();
	for($m=1; $m<12; ++$m)
	{	$shrike_weekdays[$y][$m] = weekdays_in_month_Shrike($m, $y);
	}
}

I didn't really bother with a full standard test harness. If I knew it was going to matter I would've 🙂

And mine has fewer lines! :p

And is wrong 167 times in the sample period 🙂

[Shrike]

Hmm tested and yours seems to run a bit (10th of a second?) faster 😃

Not sure how mine goes wrong though...the first code I posted was incorrect, hope your not using that. The second bit works for May, August and October 2004, too lazy to check any more 🙂

[Weedpacket]

Originally posted by Shrike
Hmm tested and yours seems to run a bit (10th of a second?) faster 😃

Not sure how mine goes wrong though...the first code I posted was incorrect, hope your not using that. The second bit works for May, August and October 2004, too lazy to check any more 🙂

Y'know, I could have sworn I was, but it turns out I wasn't. I remember checking that I had use your fixorized version, but ... oh well. Yeah, it is fixed.

I just have this dislike of assuming that a day is 86400 seconds long. Turns out there's no difference in this case, but you can imagine situations where "now+86400 seconds" is still today.

Oh; and as you noticed, every month has exactly four consecutive periods of seven days each, for a total of 28 days (and 20 weekdays). I didn't assume that in my code, but it's true, so I can.

function weekdays_in_month($month, $year)
{
	$first = mktime(0,0,1,$month,1,$year);
	// The first day of the month is also the first day of the
	// remaining days after whole weeks are handled.
	list($first_day,$days) = explode(' ',date('w t',$first));
	$weekdays = 20;

if($days==28)
	return $weekdays; // Only happens most Februarys

$weekdays += $days-29;
// Neither starts on Sunday nor ends on Saturday
if($first_day!=0 && ($first_day+$days-1)%7!=6)
{	// Adjust for weekend days.
	$weekdays += ($days<=34-$first_day)-
                 ($days>34-$first_day);
}


return $weekdays;
}