How can I use mongodump to dump out records matching a specific date range?

I solved it – the magic incantation I was looking for is:

mongodump --query "{\"ts\":{\"\$gt\":{\"\$date\":`date -d 2011-08-10 +%s`000},\"\$lte\":{\"\$date\":`date -d 2011-08-11 +%s`000}}}"