since you tell grep to quit after its first match the pipe is also closed. And that is exactly what signal 13 means:
Broken pipe: write to pipe with no readers
Here is a working example how to find all files that were modified on 1/Jan/2011
find /path/to/search -newermt 2011-01-01 \! -newermt 2011-01-01 -printf '%Td-%Tm-%TY %p\n' -quit
for more options on the output format.
PS: I am not sure, if the '!' has to be escaped as I did in my example. On my bash it works with an escaped '\!' as well as unescaped '!'.