public static function Time()
{
$base_begin = explode(' ', self::$base_begin);
$base_end = explode(' ', self::$base_end);
$test_begin = explode(' ', self::$test_begin);
$test_end = explode(' ', self::$test_end);
$base = (double) $base_end[0] + (double) $base_end[1] - ((double) $base_begin[0] + (double) $base_begin[1]);
$test = (double) $test_end[0] + (double) $test_end[1] - ((double) $test_begin[0] + (double) $test_begin[1]);
if ($test > $base) {
self::$time = $test - $base;
} else {
self::$time = 0;
}
}
