Elisabeth Achelis (January 11, 1880 – February 11, 1973)[1] was founder of the World Calendar Association in 1930 and served as its president.

She had a twin sister named Margaret,[2] and attended Brooklyn Heights Seminary and the Ogontz School in Pennsylvania.

[4] In 1929 she attended a lecture by Melvil Dewey[5] at the Lake Placid Club on the idea of a thirteen month calendar, proposed by Moses B.

Achelis started the Journal of Calendar Reform in 1931, publishing it for twenty-five years,[8] and wrote five books.

Also, Achelis wrote in 1955, "While Affiliates and Committees have over the years and still are able to approach all branches of their governments, the Incorporated (International) Association was prevented from seeking legislation in the United States lest it lose its tax exempt status.