From the past until now, Muslims have not had a single calendar, which has resulted in differences in determining Muslim holidays. The absence of an Islamic calendar globally will create chaos in the organization of time in the world, both times of worship (religion) and social activities (muamalah). This article uses the figure of Syamsul Anwar as a figure driving the global Islamic calendar in Indonesia in overcoming differences in determining Muslim holidays, and reveals how to understand the concept offered. This study explores his thoughts using works (both books, journals and other sources of information). The methodology in this research is library research where the main data source is obtained from the study of books related to this research problem, both through primary and secondary data sources.  Syamsul  Anwar  offers  several  concepts  or  principles  so  that  a  global  Islamic calendar of one day and one date throughout the world can be realized. The principles offered by him are: (1) total acceptance of reckoning, (2) transfer of imkanu rukyat, (3) having one matlak, and (4) agreeing to the international date line. By agreeing to this principle, the global Islamic calendar will soon be achieved