Here are a few possible solutions:
If you want to use the current line that you're using, it should look like this:
$end = mysql_query("SELECT * FROM `round` WHERE `left` < '$time'")or die(mysql_error());
However, you said that you wanted to compare and see if it was similar. If you wanted to do that, then this might help out:
$end = mysql_query("SELECT * FROM `round` WHERE `left` LIKE '%$time%'")or die(mysql_error());
I'm not sure if that is what you wanted to do, however that would check if $time is located anywhere in left, but I don't think that's what you meant.
You might find that you will want to use a more precise error checking method later on for MySQL queries, as some additional text so you can know where to jump to the problem.
Good luck!