The Tate Modern, Bankside, London, 4th January 2014
A palindromic date, such as today, 4-1-14, is one that is a mirror image of itself. They are said to be auspicious, particularly for choosing a date to get married. A watch dial I am currently designing (though not likely to be released till 2015) indicates when the day is a palindrome. I couldn't find any existing kind of symbol to represent it, so I drew the one in the image below.
There is some flexibility of interpretation, such as whether or not you put zeroes in, for example 01/1/10. Such auspices are also culture-specific: if your American, you'll order the numbers month-date-year; if you're Chinese it'll be year-month-date. You can even use the full four-digit year, although they are rarer and therefore more auspicious. (I look forward to 4/10/2014!)
Palindromic dates are unevenly distributed. For the last four years, we've had a spate of them, but now in 2014, they'll be much rarer, and it'll stay that way until 2020.
The most auspicious of all are those dates where all digits are the same. I remember savouring the moment of 11:11:11 11/11/11 with my greengrocer in Borough market. (Though not enough to marry him.)