I am using this code to generate yesterday's beginning of day in PST (aka America/Los_Angeles) time. I can't figure out how to convert the result to UTC.
date_default_timezone_set("America/Los_Angeles");
$time1 = date("Y-m-d H:i:s", mktime(0,0,0, date('n'), date('j')-1, date('Y')));
I tried this, but $time1 is not datetime, it's string. So the following won't work.
$time1->setTimezone(new DateTimeZone("UTC"));