Fudge factor

[Mullins, Bill]

 OED has 1977 for "fudge factor"

"Today Pushes Spring Ahead by 18 Hours" Michigan | Ironwood | Ironwood
Daily Globe | 1956-02-29 p.12 col 2.
"Today is that fudge factor jammed into the calendar every four years to
allow for time we gain on the sun during our normal calendar year."

MIT students had the same idea, under different names, earlier:
_The Tech_, May 14, 1935, p. 2 col 3.
"A benevolent and learned young man down in North Carolina has been kind
enough to inform us of an addition to the list of local slang which we
presented in the Open House issue.  He informs us, that we failed to
mention a Banjo Constant, and what is worse, to distinguish between a
Banjo Constant and a Bugger Factor.  The latter it seems, is to be added
or subtracted, while the former is a multiplication constant.  Well, we
conducted a more or less intensive survey of the Institute.  And not a
student could we find who had ever heard of a Banjo Constant.  One
freshman remarked that we probably meant a Jones constant, which is a
provincialism of the Naval Academy."