◼ At 11.11.11 on 11.11.11, the time and date will be a perfect same-numbered palindrome, reading the same backwards as forwards, an event which can only happen on one day every 100 years. - Daily Mail
Among other things, 11.11.11 will be:
... Armistice Day, celebrated around the world.
... A day of spiritual significance for those who believe the number 11 has a mystical power.
... A very special day to get married or have a birthday (especially if it's your 11th).
... Perhaps even the end of the world, according to some 'prophecy' web forums.
The reason the date is so unusual is that 11.11.11 is the only double-figure palindromic date, since there is no 22nd month.