“Every day is a school day” means the same thing as “you learn something new every day.” The saying is often associated with “the world is a/my/our classroom/school,” meaning that learning can take place outside of a school day and a school classroom.
 
“Every day is a school day” has been cited in print since at least 1921, when it was said by the Rotarian Walter S. Young, an assistant superintendant of schools at Worcester, Massachusetts.
 
   
Wiktionary: every day is a school day
Proverb
every day is a school day
1.You learn something new every day.
 
Urban Dictionary
every day’s a school day
Phrase that means the same as “you learn something new every day” - basically what someone says when the are told something they didn’t know before.
(...)
by brendan Dec 23, 2004
 
8 April 1921, Idaho Statesman (Boise, ID), “School Days,” pg. 4, col. 2:
A Rotary club speaker in Boston the other day said this:
 
“The educational forces of modern society are not confined to schools. It is a distinct feature of our time that everywhere the extension idea of education is gaining wide anr surer acceptance. To the alert man every day is a school day. He unconsciously paraphrases a historic utterance and lives by the motto, ‘The world is my school.’”
 
Google Books
September 1921, The Rotarian, pg. 162:
Education: A Factor in Attendance
By WALTER S. YOUNG
Rotarian Young is Assistant Superintendant of Schools at Worcester, Massachusetts
The educational forces of modern society are not confined to schools. It is a distinct feature of our time that everywhere the extension idea of education is gaining wide anr surer acceptance. To the alert man every day is a school day. He unconsciously paraphrases a historic utterance and lives by the motto, “The world is my school.”
 
Google News Archive
10 February 1922, Schenectady (NY) Gazette, “Uncommon Sense” by John Blake, pg. 6, col. 4:
EVERY DAY IS A SCHOOL DAY
You will never gain any knowledge unless you have the thirst for it.
 
2 November 1960, Evening World-Herald (Omaha, NE), “‘Bootstrap’ Program Director in Omaha,” pg. 23, col. 1:
The man in charge of the “bootstrap” educational program for banking employes was in Omaha Tuesday night.
 
Milton Darr. Chicago, explained: “Since there is so much to know in the business, every day is a school day.”
 
Google Books
The Bloke’s Guide to Babies
By Jon Smith
Carlsbad, CA: Hay House, Inc.
2008
Pg. 47:
Every day is a school day.
 
Google Books
When Sparrows Fall: a novel
By Meg Moseley
Colorado Springs, CO: Multnomah Books
2011
Pg. 61:
“Indeed, every day’s a school day. The world is our classroom.”
     
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Published On: Wed, Jan 4th, 2012
The Importance of Staff Training
As the old adage goes, every day is a school day and the same applies to the world of work. In a fast paced and highly competitive employment scene, it’s important to keep your staff on top of their game as well as incentivizing your business via staff training.