Today is May 12, 2021.

https://time.is/Washington,_D.C.

The United States is divided into twelve Federal Reserve Districts (Boston, New York, Philadelphia, Cleveland, Richmond, Atlanta, Chicago, St. Louis, Minneapolis, Kansas City, Dallas, and San Francisco); American paper currency has serial numbers beginning with one of twelve different letters, A through L, representing the Federal Reserve Bank from which the currency originated.

https://en.wikipedia.org/wiki/12_(number)

Federal Reserve Bank

A Federal Reserve Bank is a regional bank of the Federal Reserve System, the central banking system of the United States. There are twelve in total, one for each of the twelve Federal Reserve Districts that were created by the Federal Reserve Act of 1913.

https://en.wikipedia.org/wiki/Federal_Reserve_Bank

Anon is thinking:

[C] before [D] = 3rd District before 4th District