Chronologically, 11.11.11. is an interesting , but not unique occurrence: we had similar a configuration thirteen months ago and will have another thirteen months hence. Historically, however, 11.11.11. is a rather more significant, and bitter-sweet, marker. It was the precise date and time of the Armistice, the end of the Great War.

Of course, you are quite right that the year of the armistice was 1918. However, the precise time of the armistice was the eleventh minute of the eleventh hour of the eleventh day, i.e. 11:11 am on Nov. 11. In a host of countries which participated in the war (excluding Germany), "11.11.11' has been enshrined as the most significant marker of the war's end.
Best regards,
Michael
...no minutes in it...The signing took place in the early morning of the 11th November, 1918 and took effect at 11am.