However, regardless of language or local date formatting, I think you can figure out why February second was the day selected to pay tribute to the twin tail hair style (aka pig tails).
It’s 22:22 west coast US time on 2/2, 2017, which means that it’s as good a time as any to celebrate Twin Tail Day.
Some otaku holidays like Moe Day or Yaoi Day rely on Japanese linguistic word play or order of the day and month in the way dates are written.