Feb. 27th, at Croghan, Lewis Co., N. Y., of the Amish Men. church, Bishop MICHAEL ZEHR, at the advanced age of 89 years, 4 months and 27 days. He had 9 children, 170 grand and great-grandchildren. His wife was called away many years since. He was a good man, whose hand was ever open for the poor. In his office he was a good counselor, and was beloved by all who had the pleasure of his acquaintance. On the funeral occasion words of comfort were delivered by Peter Lemon and Jacob Vogt. The labors of our brother are ended on this earth, and he has gone to the reward of the righteous.
From: The Herald of Truth - Volume XVII, Number 4 - Apr 1880 - pages 76-78.
If he died 27 Feb 1880 as this obituary says, and was 89 y, 4 m, 27d at his death, this would make his birth at 30 Sep 1790. If the correct date of death is 26 Feb 1880, then the same age would make his birth on 29 Sep 1790.
I'll bet you are right, it's hard when even the documentation has such varied dates and numbers.