CODEWITHSUNDEEP
phpdatetimedst
ChrisFNZ
ChrisFNZ

Reputation: 617

PHP date time conversion issues related to daylight savings

I have some localisation functions within my webapp (exposed via Ajax) which enable users to display some datetime information in their own timezone as well as the timezone relating to the location of the entity the data primarily relates to.

As a result of some testing, I've discovered that whilst my code is capable of converting DB sourced date/time values accurately (i.e. including DST adjustments), the code would not calculate the correct offsets when I was using dates provided within a form. The best I've been able to achieve is converting the form date/time value to UTC but the incorrect offset is applied. This means that I need to check whether the date falls within the daylight savings range and if so, pull the datetime value back by an hour. This seems like an ugly fix and I'd appreciate it if anyone knows where I've gone wrong:

Example:

Code follows:

echo "FROM DB1:  ".$getListing['lo_deadline']."<BR />";
echo "FROM FORM1:".$in_lo_deadline."<BR />";
$frmDateTime =  DateTime::createFromFormat($this->view->user->user_datetimeformat, $in_lo_deadline,new DateTimeZone($list_tmzn));                   
echo "FROM FORM2:".$frmDateTime->format('Y-m-d h:i:s')."<BR />";
//If $frmDateTime is in daylight savings then subtract an hour to arrive at the correct UTC value                   
if ($frmDateTime->format('I'))
{
    date_sub($frmDateTime, date_interval_create_from_date_string('1 hours'));
}
echo "FROM FORM3:".$frmDateTime->format('Y-m-d h:i:s')."<BR />";                    
$dates['set_dead'] = convertUserDate($frmDateTime->format('Y-m-d h:i:s'), $this->view->user->user_datetimeformat, $user_tmzn,'UTC');

Upvotes: 1

Views: 781

Answers (1)

M A
M A

Reputation: 351

What I understand from your code, the reason why it's showing 2018-11-25 04:00:00 is because of AM/PM format. You should be using capital H instead of h in your code.

You need to understand the difference between 24 hour and 12 hour formats. 2018-11-25 04:00:00 according to your format is in AM/PM or 12 hour format, but in 24 hour format it should be 2018-11-25 16:00:00. Database time is always in 24 hour format.

Change

$frmDateTime->format('Y-m-d h:i:s')

to

$frmDateTime->format('Y-m-d H:i:s')

Note: You don't need to manually subtract an hour to calculate daylight saving time as php does it automatically.

Upvotes: 1

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