The Blackfoot optimist. [volume] (Blackfoot, Idaho) 1907-1918, 1913-03-13
Easter Date Changes Because It
Governed by the Moon

BY Garrett p. serviss IN Butte Minor
The great Christian festival of East
er, marking the anniversary of the
resurrection Of Christ falls this year
within one day of it's earliest possible
date 1t comes on Sunday, March 20.
Last year it fell on Sunday, April z
Some years it occurs several weeks
later.
All other anniversaries except East
er, and the holy days associated with
1t, fall on a fixed day of each year,
and people who are not familiar with
what is called the ecclesiastical calen-
dar are often greatly puzzled to &C.
count for the wandering Of this great
festival whose extreme dates may be
as much as five weeks apart. A late
Easter has more flowers end more
sunshine; an early one, like that OF
the present year, sometimes feels the
last chill Of the departed wintcr.
The primary reason for tho variable
date of Easter is tho fact that
it is the only great festival in Chris
tan countries that depends directly
lpon the monthly motion of tie moon
At the same time, it is affected by
the yearly motion of the sun, since it's
date is governed by the vernal equi--
nox, which is the point in the year
when the sun crosses the equator from
the southern into the northern hernis-
phere.
But the year and the month are not
commensurate lengths of time-that
Is to say there is not an even number
of lunar me nths in q year. A lunar
month is not the same as a calendar
month, but it represents the time
from one full moon to the next, which
Is, on the average, about 20 days, /
hour, Al minutes. A year, which is
measured by the apparent motion Of
the sun, IS on the average 1854 day.
Now this cannot be divided by the per-
iod Of lunar month without a re-
mainder.
In consequence, a full moon may &C.
cur at any time in tie course of an
ordinary month.
But the rule for finding the date OF
Easter is that it must fall upon the
Sunday Immediately following the first
full moon, which occurs on regular
date Of tho equinox.
Last year the first full moon fol-
lowing the equinox happened on April
l. which was Monday. The next fol-
lowing Sunday. Apri: z. was then, &C.
cordinG to tie rule, Easter day This
year the full moon Of the equinox, or
the paschal moon as it is called in the
church calendar, fall on March %,
which is Saturday, and the next day,
the twenty-third. teing Sunday, be-
comes Easter day.
Inasmuch as Christmas day, which is
celebrated as the anniversary Of the
birth Of Christ, comes at a fixed date
every year, Dec. rs, it would appear
much simpler to keep Easter also as
near fixed date as possible. 1t could
not be absolutely fixed because of the
settled custom Of celebrating it On a
Sunday, but. as the astronomer CLAW
ius pointed out centuries ago, a reason
able degree of regularity could be ill.,
troduced by making Easter the first
Sunday after the equinox without re-
gard to the phase of the moor II that
rule were adopted the date Of Easter
would still be a movable one, but its
wanderings would be kept within a
week Ct a fixed date.
The existing system Of determining
the date Of Easter is based upon a
discovery made more than 400 years
before Christ by the Greek astronomer
Melton. He found that 235 lunar
months are almost exactiy equal in
total length to 10 years OF 1854 days
each. Trere is, difference Of only |
about two Lours in the course Of the |
10 years. This period Is called the |
Metonic cycle. and its division into
years gives rise to the golden num- |
bers,' which indicate the place Of
any year In the cycle. At the begin
ming Of tie cycle, which, as used in
tie ecclesiastical calendar, Is rcckoned
from Jan. l Of the year 1, B. c.,
new moon Happened to fall On Jan. 1.
Every 10 years since then there has
been q new moon at the beginning OF |
January, but during tte intermediate
years Of the cycle the first new moon |
II the year occurs at different dates !