Death of King Nebuchadnezzar, the Babylonian emperor who conquered Jerusalem and destroyed the first Holy Temple 26 years earlier, died on the 25th of Adar of the year 3364 from creation. (Jeremiah 52:31)

Rebbetzin Chaya Mushkah Schneerson (1901-1988) of righteous memory, wife of the Lubavitcher Rebbe of righteous memory, was born on Shabbat, the 25th of Adar, in Babinovich, a town near the Russian city of Lubavitch, in the year 5661 from creation (1901). In an address delivered on the 25 of Adar of 1988 (the Rebbetzin's 87th birthday, and about a month after her passing), the Rebbe initiated an international birthday campaign, urging people to celebrate their birthdays and utilize the day as a time of introspection and making resolutions involving an increase in good deeds.

Links:
An on-line biography of the Rebbetzin
On the Jewish Birthday and the birthday customs