The changes made by Gregory corrected the drift in the civil calendar which arose because the mean Julian calendar year (exactly 365 1/4 days) was slightly too long, causing the [[vernal equinox]], and consequently the date on which Easter was being celebrated, to drift slowly forward in relation to the civil calendar and the seasons. | The changes made by Gregory corrected the drift in the civil calendar which arose because the mean Julian calendar year (exactly 365 1/4 days) was slightly too long, causing the [[vernal equinox]], and consequently the date on which Easter was being celebrated, to drift slowly forward in relation to the civil calendar and the seasons. |