Today represents the last set of repeating, single-digit dates that we'll see for almost a century (until January 1, 2101), or a millennium (mark your calendars for January 1, 3001), depending on how you want to count it.
The sum of the two-digits resulting from nine multiplied by any other single-digit number will equal nine. So 9x3=27, and 2+7=9.
Multiply nine by any two, three or four-digit number and the sums of those will also break down to (multiples of) nine. For example: 9x62=558; 5+5+8=18; 1+8=9.
Sept. 9 also happens to be the 252nd day of the year (2 + 5 +2)