“May and December can never agree” (May and December marriage proverb)

A “May-December romance” (or “May and December romance”) is when someone in the “May” or “spring” of life (youth) is romantically involved with someone in the “December” or “winter” of life (old age).
 
The saying is from a song, “An Old Man Would Be Wooing,” a ballad from at least 1818. A verse is:
 
An old man, an old man, will never do for me,
For May and December can never agree.”
 
“May and December marriages” was printed in the Public Ledger (Memphis, TN) on November 6, 1869. “Sequel to a May and December Romance in Chicago” was printed in The Evening World (New York, NY) on August 17, 1894.
   
     
The British Newspaper Archive
15 October 1818, Morning Advertiser (London, UK), “STRAND THEATRE.—The Sans Pareil,” pg. 2:   
But she, when he was suing, For ever laugh’d, and sung— An old man, old man, will never do for me. For May and December can never agree.
 
3 May 1834, Manchester (UK) Times, “Sporting Intelligence,” pg. 3, col. 7:
“May and December,” says the old song, “can never, can never agree,” ...
   
Google Books
The American Minstrel:
A Choice Collection of the Most Popular Songs, Glees, Duets, Choruses, &c.
Cincinnati, OH: J. A. James & Co.
1837
Pg. 213:
An old man, an old man, will never do for me,
For May and December can never agree.
 
Google Books 
July 1837, The American Monthly Magazine, “The Head Clerk,” pg. 73:
You know what the song says—
 
“An old, an old man
Will never do for me,
For May and December
Will never, will never agree.”
 
14 May 1839, Morning Herald (New York, NY), “Glance at New Orleans,” pg. 2, col. 4:
The marriage takes place next Saturday evening the 20th instant. This is the last new experiment of the General’s. It is said that “May and December will never agree”—we shall see.
   
OCLC WorldCat record
May and December : a tale of wedded life
Author: Catherine Anne Austen Hubback
Publisher: Philadelphia : Lippincott, Grambo & Co., 1855.
Edition/Format:   Print book : Fiction : English
 
Newspapers.com
6 November 1869, Public Ledger (Memphis, TN), pg. 1, col. 4:
M. De Lesseps, of Suez Canal celebrity, has just taken to himself, in Egypt, a young bride. Letters from that country state that the bride is a beautiful creole, twenty-two years of age. The distinguished bridegroom is sixty-four, but his years sit very lightly upon him, (...) It would seem as though the management of great public enterprises were a promoter of May and December marriages; and so it is that, if we have our Vanderbilt, Egypt has her De Lesseps.—New York World.
 
29 November 1869, Liverpool (UK) Mercury, pg. 6, col. 5:
There was a May and December marriage in Chester the other day, a farmer of 73 taking to wife the daughter of another farmer, aged 24.
     
Newspapers.com
17 August 1894, The Evening World (New York, NY), pg. 1, col. 2:
MACKIN’S WIDOW REMARRIES.
Sequel to a May and December Romance in Chicago.
(By Associated Press.)
CHICAGO, Aug. 17.—Mrs. Martha Mackin, nee Byrnes, the New Orleans young woman who married the aged millionaire, Thomas Mackin, of this city shortly before his death, and has been recently having difficulty with the other Mackin heirs over his fortune, was wedded again last night.
 
29 November 1900, Wood County Reporter (Grand Rapids, WI), “The Mother from Wisconsin,” pg. 7, col. 5:
At about 18 she visited a sister in Minneapolis, met the widower Day, then a man of 60, wealthy and with children grown, and a May-December romance ensued.
 
26 October 1905, Pittsburgh (PA) Gazette, “Divorce Suit Ends Match Based on Vision; McKeesport Damsel of 17 Wants Separation from 76-Year-Old Husband,” pg. 1, col. 6:
This May and December romance was started in Dr. Grubbs’ medical practice.
   
25 December 1913, Brooklyn (NY) Daily Eagle, pg. 1, col. 4:
MAY AND DECEMBER ROMANCE SHATTERED
Mrs. Caroline Brummer, 73, Says Husband of 30 Assaulted Her.
 
Newspapers.com
5 August 1922, Daily News (New York, NY), pg. 1, col. 3:
OLD STORY.—Another May-December romance was revealed yesterday as shattered when Edith L. Ransom, twenty-three, sued J. B. Woodward, sixty, for $100,000.
 
OCLC WorldCat record
May-December romance
Author: John Corbett; Arts and Entertainment Network.; A & E Home Video (Firm)
Publisher: Burlington, VT : A & E Home Video, ©1999.
Edition/Format:   DVD video : VHS tape : English
Summary:
Explores psychological and sociological explanations for attraction and marriage among couples sharing unusual age differences
 
Urban Dictionary
May-December Romance
A May-December Romance is an instance of the romantic involvement of two parties between whom there is a considerable age difference, often because one individual has an ulterior motive, such as money, status, etc.

The reasoning behind this designation is that while one person is young and in the “Spring” of his or her life (thus, “May”), the other is in “Winter” (ergo, “December”).
 
However, there are many instances, as in the case of my own clandestine affair with the most wonderful woman in the world, where the age difference is either inconsequential or isn’t even a considerable enough gap to constitute a May-December Romance.
(...)
by “Bun Bun” December 08, 2005
     
OCLC WorldCat record
The Politics of Aging in the May-December Romance Plot
Author: Timothy Shary
Edition/Format: Article Article
Publication: Quarterly Review of Film and Video, v31 n7 (20141003): 669-678
 
verywell mind
May-December Marriage—Marriage Age Difference
Some Prefer to Use the Term December-May Marriage
By Sheri Stritof
Updated November 17, 2017
Generally considered to be an unconventional choice, a May-December marriage is one in which one spouse is significantly older than the other spouse.
 
Significantly older is usually considered 11 years or more age difference.
 
“May” refers to the younger spouse in the spring of life, while “December” refers to the older spouse who is in what is described as the winter of life.
 
While most May-December marriages are generally accepted by society, now and then such a marriage creates a negative response