使用 PHP 在 MySQL 数据库中从 UTC 正确转换为时区

Question

I see that a stored date value in phpmyadmin is 2020-03-03. In PHP, I set the default timezone to UTC and the user's timezone to America/New_York:

date_default_timezone_set('UTC');
$userTimeZone = new DateTimeZone('America/New_York');

I retrieve my date from the database, set the timezone on the date, and make it into a string. It now equals a day earlier. (03-02-2020)

$dateNeeded = new DateTime($row['dateNeeded']); 
$dateNeeded->setTimeZone($userTimeZone);
$dateNeededStr = $dateNeeded->format('m-d-Y');

What did I do incorrectly here?

Answer 1

It is not incorrect. Your date is stored without the time component, which means when you put it in a DateTime constructor, it will be created as midnight ( $dateNeeded = new DateTime($row['dateNeeded']) will have the value of 2020-03-03 00:00:00 .

That's in UTC timezone because you defined it so at the start. So when you change the timezone, it will move back (as New York is UTC - 5) and gain the value of 2020-03-02 19:00:00 .

Since you're only outputting the date in your format (and not the time), it comes out as a day early.

Answer 2

Dont use date_default_timezone_set('UTC'); because MySQL server will use server timezone not UTC,

In example,

Your server time zone is GMT +2

And you set your server timezone to GMT +0;

Then you read your date on database which stored on GMT + 2 time zone

When you try to convert it to other timezone, eg GMT + 5,

It will shift 7 hour not 5 hour