1、Prior to A.D. 325, Easter was variously celebrated on different days of the week, including Friday, Saturday, and Sunday. In that year, the Council of Nicaea was convened by emperor Constantine. It issued the Easter Rule which states that Easter shall be celebrated on the first Sunday that occurs after the first full moon on or after the vernal equinox. However, a caveat must be introduced here. The full moon in the rule is the ecclesiastical full moon, which is defined as the fourteenth day of a tabular lunation, where day 1 corresponds to the ecclesiastical New Moon. It does not always occur on the same date as the astronomical full moon. The ecclesiastical vernal equinox is always on March 21. Therefore, Easter must be celebrated on a Sunday between the dates of March 22 and April 25.

2、翻译：在公元325年之前，复活节的庆祝时间可以是一周中不同的时间，而这些时间包括星期五、星期六和星期天。在那些年里，康斯坦丁大帝组建了尼西亚理事会。这个理事会制定了复活节的标准：复活节应该在第一个满月后或是春分后的第一个星期进行庆祝。在这里，我们要作一下解释。在规定中所指的“满月”是基督教的满月，而“满月”的时间定在阴历月份的第十四天，那么，这个月的1号就是基督教的“新月”。由于天文满月，复活节的日期不会是每年的同一天。另外，基督教的“春分”通常是3月21日。因此，复活节必须在3月22日-4月24日之间的其中一个星期天进行庆祝。