Two books about the Armenian calendar were published in the Armenian printing house of Amsterdam called “Sourb Hìmiaøin òu Sourb Sargis Xörawar” (“Holy Etchmiadzin and St. Sargis the Commander”). The first book was published twice in 1668. It was called Girq Tomaraz (“The Book of Calendars”).
The second one was published, also twice consecutively, a year later in 1669. Both of these four editions are interesting first of all because they precede by a hundred years the two official regulations of the calendar of the Armenian Church made in 1774 in Etchmiadzin by the Catholicos Simeon Yerevantsi and
also the one made seventeen years earlier in 1757 in Venice by the Armenian Mekhitarian Congregation. These publications were put together and carried out by Archbishop Voskan Yerevantsi, although they were started earlier by his brother Avetis. A notable colophon of Voskan Yerevantsi in The Book of Calendars includes observations of the phases of the moon made by the author in 1668. The author established that the first full moon of spring (Easter) happened on March 18 instead of March 21 (Saturday) as calculated and given in the 532-year tables of Easter dates used by the Armenian Church.