As to be expected, pre-war cancels continued to be used at the beginning of the occupation. The most common are the circular date cancels with a long date bar of which there are several types. In some locations pre-war cancels were used well into 1943. Other pre-war cancels, such as delivery house cancels, also continued to be used.

The first major change to the cancels was the introduction of Japanese dates. The pre-war cancels had used dates based on the Christian calendar. This calendar was soon replaced by the Japanese Koki and Showa calendars.

The Koki calendar has as starting point the year 660 B.C. which is when by legend Japan’s first emperor ascended the throne. Koki dates were written day-month-year, and the war years 1942-1945 were Koki years 2602-2605. The years were often shortened in the cancels so that, for example, 1942 = 2602 = 02, or 1943 = 2603 = -3.

The Japanese also used the Showa calendar which was based on the year when Emperor Hirohito ascended the throne. That was in 1926, which is Showa year 1, and therefore, the war years 1942-1945 are Showa years 17-20. Showa dates were written year-month-day.

In a number of instances there were problems changing the date mechanisms to accommodate the Japanese dates. This resulted in cancels with the dates written in by hand.

Subsequently on Sumatra and in the Navy occupied area the names in the cancels were also changed to Japanese. On Sumatra the name of the city or town was written at the top in the cancel, the date in the middle, and in the bottom segment was written Sumatra and the name of the province. A new Japanese delivery house cancel was also introduced.

In the Navy area there was a standard cancel with at the top Dai Nippon and in the bottom segment Teikoku Seifu which together make Great Japan Imperial Government. In the middle segment was the name of the town. These cancels did not carry a date.

The towns in the Riouw Archipelago, Lingga and Anambas Islands used Japanese cancel types from the Malayan occupied areas.

A number of other cancels were also introduced during the war. For example, a cancel for use on telegraphic money orders to Japan, Japanese Kantorpos cancels, as well as a number of commemorative cancellations.

After the capitulation the pre-war cancels with Christian dates were re-introduced. However, at many locations the pre-war cancels had been lost or damaged. Hence, we see a number of provisional cancels after the war.