php date_diff / timestamp off by 31 minutes - php

Question

I've generated a timestamp using code:
date_default_timezone_set("UTC");
$timestamp = date_create("now")->getTimestamp();
echo "value=$timestamp";
I get a value:
1484800385
I [later] want to grab the difference between that value and the current time.
$timestamp = "1484800385";
echo " timestamp=$timestamp<hr>";
print_r (new DateTime("#$timestamp"));
echo "<hr>";
print_r (date_create("now",timezone_open("UTC")));
and this outputs dates - but the difference in the time is greater than what I am expecting - by half an hour. The timezones are also shown differently.
timestamp=1484800385
DateTime Object ( [date] => 2017-01-19 04:33:05.000000 [timezone_type] => 1 [timezone] => +00:00 )
DateTime Object ( [date] => 2017-01-19 05:08:32.000000 [timezone_type] => 3 [timezone] => UTC )
I tried another script. First I generated a timestamp:
date_default_timezone_set("Australia/Sydney");
echo date_create("now")->getTimestamp(); // prints 1484800977
I then copied and pasted the value shown looked at it a few seconds later, compared to the date now
date_default_timezone_set("Australia/Sydney");
$date1 = new DateTime();
$date1->setTimestamp($timestamp);
print_r($date1);
$date2 = date_create("now");
print_r($date2);
and it's still wrong - by 31 minutes.
DateTime Object ( [date] => 2017-01-19 15:42:57.000000 [timezone_type] => 3 [timezone] => Australia/Sydney )
DateTime Object ( [date] => 2017-01-19 16:22:25.000000 [timezone_type] => 3 [timezone] => Australia/Sydney )
and UTC timezone
$timestamp = 1484801882;
date_default_timezone_set('UTC');
$date1 = new DateTime();
$date1->setTimestamp($timestamp);
$date2 = new DateTime();
print_r($date1);
print_r($date2);
results in the same timezone, but the current date is 31 minutes ahead of where I expect it to be.
DateTime Object ( [date] => 2017-01-19 04:58:02.000000 [timezone_type] => 3 [timezone] => UTC )
DateTime Object ( [date] => 2017-01-19 05:33:23.000000 [timezone_type] => 3 [timezone] => UTC )
What's going on?

Answer 1

Try to setTimeZone to UTC before print
$UTC = new DateTimeZone("UTC");
$date = new DateTime("now");
$date->setTimezone( $UTC );
print_r ($date);
echo "<hr>";
print_r (date_create("now",timezone_open("UTC")));
The output is
DateTime Object
(
[date] => 2017-01-19 05:17:52.000000
[timezone_type] => 3
[timezone] => UTC
)
>DateTime Object
(
[date] => 2017-01-19 05:17:52.000000
[timezone_type] => 3
[timezone] => UTC
)