The date of purim
Rabbi Zev Leff, Shlita, points out that Purim is unique in that the Holiday is celebrated by some Jews on Purim (14 Adar) --and other Jews on Shushan Purim (15 Adar). If Purim is a day in which we emphasize our unity--then shouldn’t we be on the exact same page?!
That is the point of Purim--to teach us that even if we are not doing the same thing--that is fine--as long as we are all doing what the Ribbono Shel Olam wants of us!
Rabbi Ozer Alport, Shlita quoted in Hakhel Newsletter