Completing a calendar of Japanese origin, Harumi SHIBUKAWA named his calendar the Yamatoreki (Yamato calendar), with taking into account the difference of longitude between China and Japan after making his own astronomical observations based on the Jujireki (Juji calendar) in China.
渋川春海は、中国の授時暦を元に自ら観測して求めた日本と中国との里差（経度差）を加味して、日本独自の暦法を完成させ、大和暦（やまとれき）と命名した。