On Japanese Maritime Self-Defense Force ships, curry is traditionally served on Friday.
The JMSDF inherited the custom from the Imperial Japanese Navy, where curry became a practical shipboard meal. It could be prepared in large quantities, stored ingredients were useful on long voyages, and the dish supplied nutrition when fresh vegetables were difficult to obtain. Curry was also associated with efforts to prevent beriberi, a deficiency disease linked to inadequate thiamine.
The Friday schedule has a practical navigational purpose as well as culinary appeal: a recurring weekly meal helps sailors keep track of the days during extended deployments. The tradition continued after the JMSDF was established in 1954.
Friday curry is not one standardized recipe. Individual ships and units develop their own versions, often competing informally over flavor. Japanese naval curry is commonly served with rice and may include beef or chicken, potatoes, onions, carrots, roux, and pickled vegetables. Monday, Wednesday, and Sunday are not the established curry day.