Because the Horyakureki (Horyaku calendar) was deemed to be inadequate, the bakufu (Japanese feudal government headed by a shogun) decided to replace it with a new calendar by adopting Western astronomy; consequently, the bakufu employed Yoshitoki TAKAHASHI as the "Bakufu Tenmongata" (official astronomer to a shogun) and asked him to reform the calendar with Shigetomi HAZAMA, an astronomer who had studied under the same teacher.
宝暦暦が出来の悪い暦法であったことから、幕府は西洋天文学を取り入れた暦法に改暦をしようとし、高橋至時を幕府天文方に登用し、同門の間重富とともに改暦の準備に当たらせた。