Very confusing issue with date and strtotime

Question

Even though i'm working with php from a long time now this issue is making me really confused. Let me explain whats going on, Suppose i'm booking an appointment for a Client at: 2019-03-31 10:00:00 and the appointment is going to be of 15 minutes so what i do is i do add these 15 minutes to the starting time of appointment which is 10:00:00, so that will turn up to be: 10:15:00 ending time of appointment, now what is happening is "ONLY" with date: 2019-03-31 (31st only) the date functionality is adding an additional hour to the time it supposed to be so instead of: 10:15:00 it changes to: 11:15:00, i did check everywhere there is no additional code above this code to change the hour i did add the below exact script main file is using in another file on same server and that just works fine with same date and same timing:

$txtstart_date = '2019-03-31';
$day_time = '10:00';
$hrmin = explode(":",$day_time);
$hours = '0';
$minut = '15';

$selected_date_time = new DateTime($txtstart_date.' '.$day_time.':00');
$selected_date_time = $selected_date_time->format('Y-m-d H:i:s');
$selected_hours = new DateTime($selected_date_time);
if($hours){
$selected_hours = $selected_hours->modify('+'.$hours.' hours');
}

if($minut){
    $selected_hours = $selected_hours->modify('+'.$minut.' minutes');
}
$selected_hours = $selected_hours->format('Y-m-d H:i:s');

echo date('Y-m-d H:i:s',strtotime($selected_hours));

it would be really great if anyone could clear the doubt here.

Summer time I think is your issue. Clocks change on the 31st of March this year — RiggsFolly, Mar 28 '19 at 19:20
Ah that is kind of making a sense to me now, that really does make a sense... any solution to this how can i avoid this from happening? cause i just need exact hours and not let the php to consider any summer time change... and yes the clock will be changed to 1 hour forward for where site is located. — Arsh Singh, Mar 28 '19 at 19:24
THis may be worth a read https://stackoverflow.com/questions/2532729/daylight-saving-time-and-time-zone-best-practices — RiggsFolly, Mar 28 '19 at 19:44

score 2 · Accepted Answer · answered Mar 28 '19 at 19:40

As mentioned by RiggsFolly, the problem might be the summer time. To prevent PHP to do weird stuff, do all the modification in one step. So you skip the part of parsing a string to a date, format it back to a string and parse it again as date:

$txtstart_date = '2019-03-31';
$day_time = '10:00';
$hours = '0';
$minutes = '15';
$datetime = $txtstart_date . ' ' . $day_time;

echo DateTime::createFromFormat('Y-m-d H:i', $datetime)
    ->modify('+' . $hours . ' hour')
    ->modify('+' . $minutes . ' minute')
    ->format('Y-m-d H:i:s');

If you need the same date twice so you can modify one, just clone it:

$baseTime = DateTime::createFromFormat('Y-m-d H:i', $datetime);
$toBeModified = clone $baseTime;

echo $baseTime->format('Y-m-d H:i:s') . PHP_EOL;

echo $toBeModified
    ->modify('+' . $hours . ' hour')
    ->modify('+' . $minutes . ' minute')
    ->format('Y-m-d H:i:s') . PHP_EOL;

It's also possible to change the used timezone of a DateTime object (which can be pretty useful in a database context when the dates stored in the database are utc):

echo DateTime::createFromFormat('Y-m-d H:i', $datetime, new DateTimeZone('Europe/London'))
    ->setTimezone(new DateTimeZone('UTC'))
    ->format('Y-m-d H:i:s');

score -1 · Answer 2 · answered Mar 28 '19 at 19:20

-1

I'm guessing it has something to do with this line right here:

if($hours){
$selected_hours = $selected_hours->modify('+'.$hours.' hours');
}

I would var_dump hours and see if it's set then trace it back to where its set.

answered Mar 28 '19 at 19:20

Lulceltech

1,662
11
22

1

This space is for answers, not guesses. – RiggsFolly Mar 28 '19 at 19:21
Yeah? It's an educated guess that is an answer to debug and solve it. Read the question then read the line of code. It's a very logical answer. – Lulceltech Mar 28 '19 at 19:22
Clocks change on 31 March. Well they do in UK. I would guess that is more likely to be the issue as the OP suggested the code works on all other days – RiggsFolly Mar 28 '19 at 19:24
You know better than to trust anyone saying their code "works" correctly. – Lulceltech Mar 28 '19 at 19:25
Can I mount my trusty steed now :) – RiggsFolly Mar 28 '19 at 19:25
1

These questions come up twice a year, when the clocks change. Just looking for a duplicate – RiggsFolly Mar 28 '19 at 19:26
And you just assume they're just in the UK? Like you said, this section is for answers, not guesses, you don't know thats the problem – Lulceltech Mar 28 '19 at 19:27
"These questions come up twice a year, when the clocks change. Just looking for a duplicate" – Lulceltech Mar 28 '19 at 19:31
And see [this comment](https://stackoverflow.com/questions/55405347/very-confusing-issue-with-date-and-strtotime#comment97531452_55405347) – RiggsFolly Mar 28 '19 at 19:31
1

@RiggsFolly 's comment is on spot, i'm located in location where time will be updated and changed to 1 hour forward ... but not actually aware of solution ... – Arsh Singh Mar 28 '19 at 19:33

Very confusing issue with date and strtotime

2 Answers2