Cleaning Day (Senjo no Hi)

What Is Cleaning Day?

October 3rd is "Senjo no Hi" (Cleaning Day) in Japan, established by the Japan Cleaning Skills Development Association, a public interest incorporated association. The date comes from a mathematical pun: "sen (1,000) is 10 to the 3rd power (jo)."

Why This Particular Wordplay?

The word "senjo" (cleaning) is broken into "sen," read as the number 1,000, and "jo," read as "power" (as in exponent), so "1,000 equals 10 to the 3rd power" (10 x 10 x 10 = 1,000) becomes a stand-in for the date October (10) 3rd.

• What "senjo" means: a general term for the act of removing dirt and grime
• The relevant technology: industrial and building cleaning using tools like high-pressure washers is the association's main field
• Environmental focus: the group promotes cleaning methods that use the power of water while minimizing environmental impact

The History of the Japan Cleaning Skills Development Association

The association was founded in 1975 as the "Japan Ultra-High-Pressure Cleaning Association" by small and medium-sized businesses specializing in cleaning industrial facilities and equipment. It was renamed the "Japan Cleaning Association" in 1981, was recognized as an incorporated association in 1994, and became a public interest incorporated association in 2012.

Tips for Marking This Day

• Clean your home's water areas or other spots that are usually hard to tackle
• Learn about cleaning technologies like high-pressure washers
• Learn about the role played by professionals who work in the cleaning industry
• Look into the origins of cleaning-related expressions and idioms

What a Math Pun Reveals About the Depth of Cleaning Work

Behind the seemingly obscure pun "1,000 equals 10 to the 3rd power" lies real pride in cleaning technology that removes dirt while supporting daily life and industry with an eye toward the environment. Let October 3rd be a day to notice the importance of "cleaning" work that so often goes unnoticed.