First things first:
Please ask your questions in english...this forum is an international effort, writing correct english as best as you can is not only polite but increases the chance of a helpful answer significantly - errors are normal and anticipated, but constructs as "CAn u plz" are frowned upon.

On to your problem:

• Use placeholders, don't concatenate SQL statements and values
• Use mysql onboard functions everywhere you can, there is an inverse function to the "unix_timestamp()" you are using, and thats "from_unixtime()"

[...]
my $stmt = $dbh->prepare("insert into test1 values(FROM_UNIXTIME(?))")
+ or die("couldn't prepare insert: " . $@);
$stmt->execute(time()-$old_time) or die ("couldn't perform insert: " .
+ $@);
[...]
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