Because the fast is moved, the fast itself falls on the anniversary of the Expulsion From Gaza.
Also, Shabbat marked 8 years since Obama became famous on Tisha B'Av at the Democrat National Convention in 2004.
These are two of the modern day calamaties we fast for.
You can add the Olympic Massacre too. It doesn't matter if the date is the same because we also have many kinnot for many other calamaties in our History such as the Crusades and other Anti-Semitic attacks throughout the year.