Usaldate

Usaldate is a term used in some programming discussions to describe compact encodings of calendar dates into integers. The goal is to minimize storage and enable fast date arithmetic by comparing integers rather than objects. There is no single canonical standard; implementations vary, but most share packing year, month, and day into a fixed-width integer and providing conversion routines to and from the Gregorian calendar.

Encoding schemes typically allocate a portion of bits to year, month, and day. A common approach uses 32-bit or 64-bit integers. For example, one widely cited scheme might store the year as a 12-bit field representing years since 2000, month as a 4-bit field (1–12), and day as a 5-bit field (1–31), yielding a compact value that can be incremented or compared efficiently. Many implementations also support arithmetic such as adding days or computing differences by leveraging the packed representation, though edge cases around leap years require careful handling.

Advantages include compact storage, faster comparisons, and simpler serialization. Limitations include calendar-specific semantics, potential loss of portability across systems with different epoch definitions, and the need for conversion to human-readable forms for display. Because usaldate is not standardized, developers often rely on tests and documentation for their particular library or project.

See also: date, timestamp, Julian day, Unix time, ISO 8601.