Here, we have collected our most commonly used Delphi functions to return holidays, observances, celebrations, historical, and other key dates. The code snippets included work well for nearly all versions of the Windows operating system. We test our code with Delphi 6, Delphi XE, and Delphi 10.1 Berlin. Our code is for the Windows operating environment. We have not, and do not plan to, adapt the code for other operating environments.