Girls' Day, also known as the day of the doll festival, is on March 3. In Japanese, it's called Hina Matsuri, and the main event is setting up a collection of hina dolls.
The hina dolls represent the Emperor, Empress, and members of the court. What you see in this photo is an emperor doll (on your left, top row), empress doll (top row, right) and three ladies in waiting.
Decorations include lanterns with paper shades (bonbori, in Japanese) and peach blossoms. Due to the historic lunar calendar's becoming skewed over the ages, peach blossoms are not naturally in bloom by March 3, but that is why commercial florists were invented, right?
The dolls can be set up any time after the New Year holidays are over, but they must be packed away as soon as the doll festival is finished. Superstition has it that to leave them out after March 3 is to doom your daughter to a life of spinsterhood.
