Um, we Presbyterians might be in some trouble here, especially if you hold to the original WCF that viewed the pope as the anti-Christ. Our (Gregorian) calendar was introduced by Pope Gregory XIII by a Papal Bull signed on February 24, 1582, so the days shifted by 10 days. It established a correction for leap year variances that had not been previously included. So, what say ye? Shall we all adopt the Julian Calendar? (Tongue firmly in cheek.)
And Josh, I think the bats have a sabbath night, though I think you need to like bugs to join them.