Unriddling the Daisho-reki Calendar

Q.27th year of Tenmei (1787) Daisho-reki [Blossom-viewing]

A feast featuring cherry blossom viewing is held with a curtain stretched around a cherry tree in full bloom. Twelve warabi (bracken) plants can be seen behind the curtain through which a servant is peeking. How do you distinguish long from short months?

7th year of Tenmei (1787) Daisho-reki
7th year of Tenmei (1787) Daisho-reki

Data

Title Creator
7th year of Tenmei (1787) Daisho-reki -
Physical data Subject (NDC)
17cm x 12cm 449.81/721.8
Note Call No.
Pasted in "Egoyomi" WA33-1

Answer