Q: Can one fulfill the mitsvah of Matanot La'evyonim (gifts to the poor) on Purim by contributing to a charity that distributes money to needy families in Israel on Purim day?
A: Most of us live in places where Purim is celebrated on the fourteenth of the Jewish month of Adar. In our neighborhoods, the commandment to rejoice on the holiday can only be fulfilled on the fourteenth of Adar. However, there are some cities in the land of Israel, such as Jerusalem, in which Purim is observed on the fifteenth of Adar rather than the fourteenth. For individuals living in those cities, celebration on any day other than the fifteenth of Adar would not 'count'.
As mentioned in another post, the mitsvah of Matanot La'evyonim (gifts to the poor) is a dimension of the general commandment to rejoice on Purim. Thus, it must be performed at the time when that mitsvah is applicable - in some areas, this means on the fourteenth of Adar, and in other areas, this means on the fifteenth. Now, for those of us who live in the Diaspora: If we can be sure that our contributions will be distributed to the poor in Israel on the fourteenth of Adar, this would certainly qualify as a fulfillment of the mitsvah of Matanot La'evyonim. However, if the money is set aside to be distributed on the fifteenth of Adar, then the charitable giving no longer has any connection to our celebration of Purim on the fourteenth, and will not 'count' as far as the mitsvah of Matanot La'evyonim is concerned.
This being said, though, let's keep in mind that the giving of charity - whether locally, in the Land of Israel, or anywhere else - is always meritorious. We should not think exclusively in terms of the technicalities of fulfilling our Purim obligation. On the contrary, as Rambam states, "there is no greater and more wondrous joy than bringing happiness to the poor, widows, orphans and converts. For one who brings joy to the hearts of the less fortunate is compared to the Divine Presence." This applies at all times and in all places.