Mu
mwaka wa 1582 Papa Gregory XIII yashyizeho kalendari nshya ari nayo ikoreshwa
magingo aya kugira ngo ikosore amakosa yari mu Julian Calendar (yari
yarashyizweho na Julius Caesar mu 46 mbere y’ivuka rya Yesu.
Icyo
gihe, intego nyamukuru yari uguhuza neza umwaka w’ikirere (solar year) n’uburyo
iminsi ibarwa.
Impamvu
itera Ethiopia guhora isigara inyuma mu bihe ni uko ikoresha calendar yabo ikomoka
kuri Alexandrian Calendar (ikoreshwa n’Abakristo ba Coptic bo mu Misiri).
Impamvu
kalendari ya Ethiopia iri inyuma imyaka 7 hafi 8, ni ukubera uko babara imyaka
y’ivuka rya Yesu (Annunciation of Christ) muri Ethiopia aho byagenwe ko yatangiye gukoreshwa mu myaka 7 mbere y’ivuka rya Yesu ugereranyije n’ukuntu Abagiriki na Gregoire
babibaraga.
Papa
Gregory XIII yakoze Gregorian Reform mu 1582, icyo gihe avanaho iminsi 10 mu
kwezi kwa 10 uwo mwaka (tariki 4/10 yakurikiwe n’itariki ya 15/10) kugira ngo
izuba n’amezi bihuze neza.
Ibihugu
byinshi byemeye guhindura, ariko Ethiopia (n’Abakristo ba Coptic bo mu Misiri)
ntibigeze bemera izo mpinduka, bagumana Alexandrian/Julian system.
Ethiopian Calendar igizwe n’amezi 13 aho amezi 12 afite iminsi 30 buri kwezi naho ukwezi kwa 13 kwitwa Pagumē, kugira iminsi 5 cyangwa 6 iyo ari umwaka wiswe (leap kurya muri kalendari isanzwe hari itariki 29 mu kwezi kwa kabiri aho kuba 28 nk’ibisanzwe.)



Biba ari ibyishimo bidasanzwe mu kurasa umwaka mushya muri Ethiopia bakawurasa buri tariki ya 11 cyangwa 12 Nzeri
