The chief rabbis of Israel and other influential rabbis have issued a statement that Lag Ba-omer, the 33rd day of the counting of the omer (which is the period of 7 weeks from the second day of Pesah until Shavuot) should be observed this year not on the 33rd day, but on the 34th day.*
Lag Ba-omer is the day when the plague that killed 24,000 of Rabbi Akiva's students during the omer period ended, and is thus a minor day of celebration. The rabbis' reasoning in moving it back by a day is that in Israel, many celebrate by building bonfires on the evening of Lag Ba-omer, and since this year this would be Saturday night, there would be mass desecration of the Shabbat in preparing bonfires. (To be fair, I am not aware that there has been a precedent for "moving" Lag Ba-omer; it fell on Sunday last year as well.)
The idea of relocating the celebration is mostly academic; what is more interesting to me is the fact that Judaism is not a centralized religion. We have no pope, nobody who can command something that all will follow. No matter which influential rabbis issue decrees, there will be some who reject their opinions. For sure, on Saturday night in Israel there will be bonfires, by secular Israelis who don't care what the rabbinate says, and Haredi groups for whom the merely Orthodox rabbinate is inconsequential.
But this is one of the major strengths of Judaism: our decentralization made us portable and democratic. There's no hierarchical bureaucracy in Judaism since the destruction of the Temple in Jerusalem 70 CE. And that simple fact has made it possible for us as a people to survive 2,000 years more than we might have, through exile and dispersion.
I'll be marking Lag Ba-omer on Sunday, like most of the Jewish world.
*The word "lag" is an abbreviation for 33 - the Hebrew letter "lamed" has a numerical value of 30, and "gimmel" has a value of 3. Hence, lamed + gimmel = "lag" = 33. The vowel has no value. 34 would be lamed + dalet, and therefore is pronounced "lad."