First day cover

A first day of issue cover or first day cover (FDC) is a postage stamp on a cover, postal card or stamped envelope franked on the first day the issue is authorized for use within the country or territory of the stamp-issuing authority. Sometimes the issue is made from a temporary or permanent foreign or overseas office. There will usually be a first day of issue postmark, frequently a pictorial cancellation, indicating the city and date where the item was first issued, and "first day of issue" is often used to refer to this postmark. Depending on the policy of the nation issuing the stamp, official first day postmarks may sometimes be applied to covers weeks or months after the date indicated.

Postal authorities may hold a first day ceremony to generate publicity for the new issue, with postal officials revealing the stamp, and with connected persons in attendance, such as descendants of the person being honored by the stamp. The ceremony may also be held in a location that has a special connection with the stamp's subject, such as the birthplace of a social movement, or at a stamp show.

Computer vended postage stamps issued by Neopost had first-day-of-issue ceremonies sponsored by the company, not by an official stamp-issuing entity. Personalised postage stamps of different designs are sometimes also given first-day-of-issue ceremonies and cancellations by the private designer. The stamps issued by private local posts can also have first days of issue, as can artistamps.

Event covers, instead of marking the issuance of a stamp, commemorate events. A design on the left side of the envelope (a "cachet") explains the event or anniversary being celebrated. Ideally the stamp or stamps affixed relate to the event. Cancels are obtained either from the location (e.g., Cape Canaveral, Anytown) or, in the case of the United States, from the Postal Service's Cancellation Services unit in Kansas City.

The earliest known use (EKU) of a stamp may or may not be the same as the first day of issue. This can occur if:

...
Wikipedia