PHP date modifications

dateModify.php

<?php

function test($timeOffsetMS)
{
        $modification = sprintf('-%s msec', $timeOffsetMS);
        echo 'Modificator:  ' . $modification . PHP_EOL;

        $time = 1604503053.0000; // microtime(true);
        $timeString = sprintf('%0.6F', $time);
        echo 'Source:       ' . $timeString . PHP_EOL;

        $time = \DateTimeImmutable::createFromFormat('U.u', $timeString);
        echo 'Formatted:    ' . $time->format('U.u') . PHP_EOL;

        $time = $time->modify($modification);
        echo 'Modified:     ' . $time->format('U.u') . PHP_EOL;
}

test(2000);
test(2001);

result.md

Modificator:  -2000 msec
Source:       1604503053.000000
Formatted:    1604503053.000000
Modified:     1604503051.000000

Modificator:  -2001 msec
Source:       1604503053.000000
Formatted:    1604503053.000000
Modified:     1604503051.-01000