Gregorian calendar
This made the seasons get out of track with the calendar.  For example, as the centuries went by, the equinox (when day and night are the same length) was happening earlier and earlier than its traditional date, March 21. It was the calendar that was wrong, not the earth's orbit. By the 1500s, it was starting around March 11, ten days 'too early' according to the calendar. To farmers, this did not matter because they worked to the seasons rather than to the calendar. But it mattered a lot to the Christian church because the date of Easter is calculated from the equinox being on 21 March. So Pope Gregory XIII declared that the calendar must skip ten days in 1582.