SN 2004dh:

This SN was discovered by LOSS 
(<a href="http://cfa-www.harvard.edu/iauc/08300/08375.html#Item2> 
(IAUC 8375)</a> on July 21, 2004, but was actually already visible
on July 11, 2004, and absent on June 30, 2004, so at most 21 after
explosion when reported.