Incorrect diffInMonths laravel Carbon between Feb 1 and Mar 1

Question

I found a weird result when I use diffInMonths of laravel Carbon. Can anyone explain for me why it works like this. Is it a bug? And how to get it correct.

$d1 = new Carbon('2018-02-01');
$d2 = new Carbon('2018-03-01');
dd($d1->diffInMonths($d2));

Output was: 0 (Expected: 1)

BUT

$d1 = new Carbon('2018-02-02');
$d2 = new Carbon('2018-03-02');
dd($d1->diffInMonths($d2));

Output was: 1

My setting timezone is "Asia/Ho_Chi_Minh" (GMT +7). PHP Version 7.0.22. OS: Ubuntu Server 16.04

This weird result happends only between February 1 and March 1, other months result as expected.

I also try date_diff instead of Carbon

$d1 = new \DateTime('2018-02-01');
$d2 = new \DateTime('2018-03-01');
$diff = date_diff($d1,$d2);
dump($diff->m);
dump($diff->d);
die;

It returns months: 0, and days: 28 (Not month: 1, days: 0 as expected)

So the problem may be from PHP not from Carbon.

Have you tried `dd($d2->diffInMonths($d1));` it's might be due to wrong order of difference calculation :D — Sagar Gautam, Jan 06 '18 at 04:10
$d2->diffInMonths($d1) return the same result. I use PHP 7.0 on Ubuntu server 16.04 — Vũ Nhật Anh, Jan 06 '18 at 04:27
Same occurring for "01-11-2018" and "01-12-2018" also, any reason why? — Arun J, Jan 03 '20 at 05:27

score 2 · Answer 1 · answered Apr 12 '22 at 06:14

Very peculiar behaviour:

$jan = new Illuminate\Support\Carbon("2022-01-01");
$feb = new Illuminate\Support\Carbon("2022-02-01");
$mar = new Illuminate\Support\Carbon("2022-03-01");

$feb->diffInMonths($mar); // 0
$feb->floatDiffInMonths($mar); // 1.0

$jan->diffInMonths($mar); // 1
$jan->floatDiffInMonths($mar); // 2.0

Solution

Use intval on floatDiffInMonths:

intval($feb->floatDiffInMonths($mar)); // 1
intval($jan->floatDiffInMonths($mar)); // 2

score 1 · Answer 2 · answered Jan 06 '18 at 05:45

1

You should set timezone in Carbon, Now it works:

   Carbon::now(new \DateTimeZone('Asia/Ho_Chi_Minh'));
    $d1 = new Carbon('2018-02-01');
    $d2 = new Carbon('2018-03-01');
    dd($d1->diffInMonths($d2));

answered Jan 06 '18 at 05:45

parastoo

2,211
2
21
38

It still returns 0. Actually my global setting timezone is 'Asia/Ho_Chi_Minh' already. I'm using PHP version 7.0.22 & laravel 5.2. Are there any bugs here? – Vũ Nhật Anh Jan 08 '18 at 02:22
when I used your codes it returned zero but with these codes returned 1,My PHP version is same and laravel version is 5.5 – parastoo Jan 08 '18 at 05:26

score 1 · Answer 3 · answered Jan 10 '18 at 21:57

1

The code you provided should work. Although you can try alternative of Carbon. Try DateTime

$d1 = new DateTime('2018-02-01');
$d2 = new DateTime('2018-03-01');
$diff = date_diff($d1,$d2);
dd($diff->m);

answered Jan 10 '18 at 21:57

Your code return the same results with Carbon, the output was 0. Maybe the error cause by my PHP Environment not the fault of Carbon. – Vũ Nhật Anh Jan 11 '18 at 01:57

score 1 · Answer 4 · answered Mar 01 '19 at 07:06

I think setting the timezone to UTC should solve this. I had the same problem when the timezone was set to Europe/Zurich:

>>> $last = new \Carbon\Carbon('2019-02-01');
=> Carbon\Carbon @1548975600 {#2381
     date: 2019-02-01 00:00:00.0 Europe/Zurich (+01:00),
   }
>>> $now = (\Carbon\Carbon::now())->day(1)->setTime(0, 0, 0);
=> Carbon\Carbon @1551394800 {#2371
     date: 2019-03-01 00:00:00.0 Europe/Zurich (+01:00),
   }
>>> $now->diffInMonths($last)
=> 0

After changing the timezone to UTC:

>>> $last = new \Carbon\Carbon('2019-02-01', 'UTC');
=> Carbon\Carbon @1548979200 {#2380
     date: 2019-02-01 00:00:00.0 UTC (+00:00),
   }
>>> $now = (\Carbon\Carbon::now('UTC'))->day(1)->setTime(0, 0, 0);
=> Carbon\Carbon @1551398400 {#2394
     date: 2019-03-01 00:00:00.0 UTC (+00:00),
   }
>>> $now->diffInMonths($last)
=> 1

score 0 · Answer 5 · answered Jan 03 '20 at 09:02

I encountered the same thing, but the above methods doesn't work for me. So I write this and it works perfectly fine.

$prevMonth = Carbon::parse("01-02-2019");
$thisMonth = Carbon::parse("01-03-2019");
$part1 = ($prevMonth->format('Y') * 12) + $prevMonth->format('m');
$part2 = ($thisMonth->format('Y') * 12) + $thisMonth->format('m');
$diff = abs($part1 - $part2); // To make the result always positive abs()

Result:-

1 // with abs()
-1 // without abs()

Umid Bazarov · Answer 6 · 2021-03-11T07:54:18.957

The same story, finally wrote my own function for calculating month difference:

function month_diff(\Carbon\Carbon $date1, \Carbon\Carbon $date2){
$ts1 = $date1->startOfDay()->getTimestamp();
$ts2 = $date2->startOfDay()->getTimestamp();

$year1 = intval(date('Y', $ts1));
$year2 = intval(date('Y', $ts2));

$month1 = intval(date('m', $ts1));
$month2 = intval(date('m', $ts2));

$day1 = intval(date('d', $ts1));
$day2 = intval(date('d', $ts2));

$res = (($year2 - $year1) * 12) + ($month2 - $month1) - (($day2 >= $day1) ? 0 : 1);

return $res >= 0 ? $res : 0; }

here, pay attention to the days of the month too, also may take time into account too.

Incorrect diffInMonths laravel Carbon between Feb 1 and Mar 1

6 Answers6

Linked