Figuring the Start of the Week with PHP

Tuesday, April 4. 2006

Figuring the Start of the Week with PHP

I have a time keeping utility written in PHP and MySQL. To make a query of the hours recorded so far in a given week, I needed to determine the start date of the week, in the MySQL format of 'YYYY-MM-DD HH:MM:SS'. I had been using this code:

date('Y-m-d H:i:s', mktime(0, 0, 0, date('m'), date('d')-date('w'), date('Y')));

It was successfully giving me midnight on Sunday for my code. Until the change to daylight savings time reared its ugly head (why can't we stay on DST all year?). This week that piece of code gave me '2006-04-01 23:00:00', so the rest of my code decided to include some time from Saturday.

I worked through a couple variants, but settled on this replacement:

date('Y-m-d', mktime(1, 0, 0, date('m'), date('d')-date('w'), date('Y'))) . ' 00:00:00';

This code adds an hour to the time computation. So the errant Saturday at 11PM gets returned to Sunday at midnight. Other weeks will show 1AM, and the switch back to standard time might show 2AM. Since I always want midnight, the simplest thing seemed to be to drop the time off the date function output entirely and just set it to midnight in the string.

Posted by Mike Boone in Tech at 07:01 | Comments (14) | Trackbacks (0)

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very useful. thanks!

#1 tim on 2009-02-23 21:37 (Reply)

Thanks, exactly what I was looking for.

#2 brandon (Homepage) on 2009-04-02 22:07 (Reply)

Great stuff!

However how do you make it find the start of next week???

Cheers

#3 Gin on 2009-05-29 07:47 (Reply)

I have not tried this, but you could try just adding 7 to the day calculation:

date('d')-date('w')+7

#3.1 Mike Boone (Homepage) on 2009-05-29 08:14 (Reply)

Hi Mike, thanks for getting back to me. Havin a bit of trouble with this. My code looks like this:

$weekStart = date(mktime(1,0,0,date('m'), date('d')-date('w'), date('y')));

And then I have the next days eg:

$day2 = date(mktime(1,0,0,date('m'), date('d')+1-date('w'), date('y')));

I tried what you said and tried changing my +1 to 7 but the date stays on the start of the current week. Confusing! :S

Cheers

#3.1.1 Gin on 2009-05-29 08:22 (Reply)

This is what I tried:

date('Y-m-d', mktime(1, 0, 0, date('m'), date('d')-date('w')+14, date('Y')))

That produces 2009-05-24 as expected.

Then this:

date('Y-m-d', mktime(1, 0, 0, date('m'), date('d')-date('w')+7, date('Y')))

That produces 2009-05-31, the start of next week.

Hope that helps.

#3.1.1.1 Mike Boone (Homepage) on 2009-05-29 08:28 (Reply)

No way, it was all my fault! I was using the start of week variable for calculation for the rest of the days. I wasn't acutally displaying, hence it didnt change.

Great to see a blog that is active. Excellent work, thanks

#3.1.2 Gin on 2009-05-29 08:27 (Reply)

Glad you got it working!

#3.1.2.1 Mike Boone (Homepage) on 2009-05-29 08:29 (Reply)

Hi Gin, I accidentally deleted your last comment. Anyway, I think date('H:i:s') should always give you the current time, daylight savings or not. I guess it depends on how your timing function works as to whether a daylight savings change would affect it. If it's running during the time of night your computer changes its time, it would be worth testing.

#3.2 Mike Boone (Homepage) on 2009-05-29 10:19 (Reply)

No worries mate. Did a bit of digging and it appears as though that will be effected by timezones. But thinking about it, if your using a local php server then it will change at the same time as the rest of the worlds clocks. I'll keep an eye on it. cheers

#3.2.1 Gin on 2009-05-29 10:48 (Reply)

Simplest:

strtotime("last Saturday + 1 day")

this returns the following:

on Sunday: returns midnight
on Monday: returns last Sunday's date
...
on Saturday: returns 6 days ago

#4 Tomer Chachamu on 2009-11-01 06:27 (Reply)

I'd set it up as a function.

##
function weekfinder($dformat, $date)
{
$date_parts = explode($dformat, $date);
$dtemp = date("N",mktime(0,0,0,$date_parts[0],$date_parts[1],$date_parts[2]));
if($dtemp == 1){
return date("m/d/Y",mktime(0,0,0,$date_parts[0],$date_parts[1],$date_parts[2]));
}elseif($dtemp != 1){
$dtsub = ($dtemp -1);
return date("m/d/Y",mktime(0,0,0,$date_parts[0],$date_parts[1] - $dtsub,$date_parts[2]));
}
}

$var = weekfinder("/", $datevar);
##
This does not require any hour specifications

#5 Ian B on 2009-11-06 05:30 (Reply)

Just a quick - thanks solved a problem of mine

#6 Elija on 2009-12-08 02:53 (Reply)

easier :

$data['firstDay'] = date("m/d/Y", mktime(0, 0, 0, date("m"), date("d") - date("w"), date("Y")));

$data['lastDay'] = date("m/d/Y", mktime(0, 0, 0, date("m"), date("d") - date("w") + 6, date("Y")));

#7 pepe lucho on 2010-07-26 13:04 (Reply)

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