Father Roquelaure had studied at Saint-Sulpice Seminary in Paris when he was young. That was not unusual; many people had attended that school, including Talleyrand.
Beside the seminary stood a church. Along its north-south central axis ran a brass-inlaid line. Every spring equinox, sunlight shone through an opening in the southern wall and fell upon the Rose Line. Taking that day as the marker, the first Sunday after the first Full Moon thereafter was considered Easter. Some might find that troublesome. Why could it not have a fixed date, like National Day or a birthday?
Ancient calendars were highly inaccurate. The Romans only wanted summer and cast aside the harsh winter, so a year had only ten months, and even those changed with political circumstances. It was not until Gaius Julius Caesar adopted the calculations of mathematicians and astronomers from Alexandria, Egypt, that the Julian Calendar replaced the old Roman calendar on January 1, 45 BC. The year was divided into twelve months, with long and short months alternating, a leap year every four years, 365 days in an ordinary year and 366 in a leap year, for an average year length of 365.25 days.
Yet as accumulated errors grew larger over time in actual use, they eventually caused the phenomenon of the "drifting spring equinox." In other words, the equinox that ought to have fallen on March 21 did not actually fall on that day, sometimes arriving more than ten days early. That was why the Rose Line was needed for correction.
April Fools' Day originated in France. The Sun followed its own course, but the first day of the new year was decided by people. To many traditionalists, New Year's Day was April 1, after Easter, and this tradition had lasted nearly a thousand years. In 1582, King