In an e-mail from my coworker (who is around the same age as my mother), the following:
“How could we have missed it? March 15 was Penis Day in Japan. Here are the photos. The actual festival is called Honen Matsuri.
Celebrated every March 15 in Komaki, a town about 45 minutes north of Nagoya, Japan, this is the time of year where folks haul out a large wooden penis to give three cheers to fertility and renewal.
The custom is an old one that is connected to bringing about a good harvest and having babies.”
Thanks D!