paschal moon, so that if the 14th of the paschal moon falls on a
Sunday then Easter must be celebrated on the Sunday following; _3rd_, the
paschal moon is that of which the 14th day falls on or next follows the day
of the vernal equinox; _4th_ the equinox is fixed invariably in the
calendar on the 21st of March. Sometimes a misunderstanding has arisen from
not observing that this regulation is to be construed according to the
tabular full moon as determined from the epact, and not by the true full
moon, which, in general, occurs one or two days earlier.

From these conditions it follows that the paschal full moon, or the 14th of
the paschal moon, cannot happen before the 21st of March, and that Easter
in consequence cannot happen before the 22nd of March. If the 14th of the
moon falls on the 21st, the new moon must fall on the 8th; for 21 - 13 = 8;
and the paschal new moon cannot happen before the 8th; for suppose the new
moon to fall on the 7th, then the full moon would arrive on the 20th, or
the day before the equinox. The following moon would be the paschal moon.
But the fourteenth of this moon falls at the latest on the 18th of April,
or 29 days after the 20th of March; for by reason of the double epact that
occurs at the 4th and 5th of April, this lunation has only 29 days. Now, if
in this case the 18th of April is Sunday, then Easter must be celebrated on
the following Sunday, or the 25th of April. Hence Easter Sunday cannot
happen earlier than the 22nd of March, or later than the 25th of April.

Hence we derive the following rule for finding Easter Sunday from the
tables:--_1st_, Find the golden number, and, from Table III., the epact of
the proposed year. _2nd_, Find in the calendar (Table IV.) the first day
after the 7th of March which corresponds to the epact of the year; this
will be the first day of the paschal moon, _3rd_, Reckon thirteen days
after that of the first of the moon, the following will be the 14th of the
moon or the day of the full paschal moon. _4th_, Find from Table I. the
dominical letter of the year, and observe in the calendar the first day,
after the fourteenth of the moon, which corresponds to the dominical
letter; this will be Easter Sunday.

TABLE IV.--_Gregorian Calendar._

|-----------------------------------------------------|
|Days.| Jan. | Feb. |March. |April. | May. | June. |
|-----+-------+-------+-------+-------+-------+-------+
| | E |L| E |L|