The armistice was signed at 5:00 a.m. to establish the ceasefire time for exactly 11:00 a.m. the same day. Thus, it became the 11th Hour of the 11th Day of the 11th Month. No "minutes" were recognized.
Google agrees:
The misconception that the Armistice for World War I happened at 11:11 is incorrect; it happened at exactly 11:00 AM on the 11th day of the 11th month of 1918. The number 11:11 is often a retropsective and erroneous association made by people fascinated with patterns and not the actual time the fighting stopped. The 11 AM time was chosen because it was a simple and convenient time for the agreement to take effect after it was signed at 5 AM that morning.
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