ANSWER

A.June 1st (The photo was taken for the first time in Japan)

　Nariakira Simazu ,who was Satsuma clan lord, took photos on June 1st.
Photographic Society of Japan made that day in 1951.

　Now a commemorative photo studio is opened to convey pleasure and the importance of the photograph on that day.

　Also countries of approximately 20% of the world establish June 1st as Children's Day according to the agreement with Children's day at the World WelfareMeeting for children Genevva in 1925.

Other than June 1 is the day to celebrate cheese.