Summer Litter, 2010:
Above video was taken August 10th of 2010. These squirrels were born on July 18th, 2010 — making them 23 days old here.

Summer Litter, 2009 — Above video taken on August 11, 2009.
These babies were born on July 21st, 2009 — making them 21 days old in this video.
(Penny placed against corner of window for visual size reference.)