Square Root Day is an

unofficial holiday A holiday is a day set aside by custom or by law on which normal activities, especially business or work including school, are suspended or reduced. Generally, holidays are intended to allow individuals to celebrate or commemorate an event or tra ...

celebrated on days when both the day of the month and the month are the

square root In mathematics, a square root of a number is a number such that ; in other words, a number whose ''square'' (the result of multiplying the number by itself, or  ⋅ ) is . For example, 4 and −4 are square roots of 16, because . E ...

of the last two digits of the year. For example, the last Square Root Day was April 4, 2016 (4/4/16), and the next Square Root Day will be May 5, 2025 (5/5/25). The final Square Root Day of the century will occur on September 9, 2081. Square Root Days fall upon the same nine dates each century. Ron Gordon, a

Redwood City, California Redwood City is a city on the San Francisco Peninsula in Northern California's Bay Area, approximately south of San Francisco, and northwest of San Jose. Redwood City's history spans its earliest inhabitation by the Ohlone people to being a ...

high school teacher, created the first Square Root Day for September 9, 1981 (9/9/81). Gordon remains the holiday's

publicist A publicist is a person whose job is to generate and manage publicity for a company, a brand, or public figure – especially a celebrity – or for a work such as a book, film, or album. Publicists are public relations specialists who ...

, sending

news release A press release is an official statement delivered to members of the news media for the purpose of providing information, creating an official statement, or making an announcement directed for public release. Press releases are also considere ...

s to world

media Media may refer to: Communication * Media (communication), tools used to deliver information or data ** Advertising media, various media, content, buying and placement for advertising ** Broadcast media, communications delivered over mass el ...

outlets. Gordon's daughter set up a

Facebook Facebook is an online social media and social networking service owned by American company Meta Platforms. Founded in 2004 by Mark Zuckerberg with fellow Harvard College students and roommates Eduardo Saverin, Andrew McCollum, Dustin M ...

group where people can share how they were celebrating the day. One suggested way of celebrating the holiday is by eating

radish The radish (''Raphanus raphanistrum'' subsp. ''sativus'') is an Eating, edible root vegetable of the family Brassicaceae that was domesticated in Asia prior to Roman Empire, Roman times. Radishes are grown and consumed throughout the world, be ...

es or other

root vegetable Root vegetables are underground plant parts eaten by humans as food. Although botany distinguishes true roots (such as taproots and tuberous roots) from non-roots (such as bulbs, corms, rhizomes, and tubers, although some contain both hypocotyl a ...

s cut into shapes with square cross sections (thus creating a "square root").

Full list

Square Root Day occurs on the following dates each century: *1/1/01 *2/2/04 *3/3/09 *4/4/16 *5/5/25 *6/6/36 *7/7/49 *8/8/64 *9/9/81

Distribution

The number of years between consecutive Square Root Days in a century is consecutive

odd numbers In mathematics, parity is the property of an integer of whether it is even or odd. An integer is even if it is a multiple of two, and odd if it is not.. For example, −4, 0, 82 are even because \begin -2 \cdot 2 &= -4 \\ 0 \cdot 2 &= 0 \\ 41 ...

: 3, 5, 7, 9, 11, 13, 15, 17. This illustrates the fact that every odd number is the difference of two consecutive squares.

References

{{Reflist Unofficial observances Observances about science Recurring events established in 1981

Full list

Distribution

See also

References