I see the Wikipedia "Flag day (computing)" [1] article references two semi-different ESR sources [2,3] to support the claim:

> This systems terminology originates from a major change in the Multics operating system's definition of ASCII, which was scheduled for the United States holiday, Flag Day, on June 14, 1966.

I don't doubt the validity, but I'm looking for other "citation worthy" sources that supplement this claim --- ideally that predate the ESR ones, so that they are unambiguously independent.

1. https://en.wikipedia.org/wiki/Flag_day_(computing)

2. http://www.catb.org/jargon/html/F/flag-day.html

3. The New Hacker's Dictionarypp. 192–