dateencoding

Dateencoding is the representation of calendar dates and times in computer systems, enabling storage, computation, and interchange. The goal is to encode a date into a form suitable for storage, comparison, arithmetic, and exchange between systems. Common encoding schemes include epoch-based encodings such as Unix time, which stores the number of seconds elapsed since 1970-01-01 UTC; 32-bit implementations face the Year 2038 problem, while 64-bit variants extend the range. Another class uses calendar date strings per ISO 8601, typically formatted as YYYY-MM-DD with optional time and time zone, frequently used for interoperability. The Julian Day Number encodes a date as a continuous day count from a fixed epoch in the distant past and is used in some scientific contexts.

In databases and programming languages, dates may be stored as binary date types (internal formats), as textual ISO strings, or as integers representing elapsed time. Time zones and daylight saving time complicate encoding; often a normalized form in UTC is stored with a separate offset or zone identifier. Some systems use Windows FILETIME or OLE Automation dates, different reference epochs and units. The term date encoding can also refer to encoding a date into a compact bit-field, packing year, month, and day into a single integer for space-efficient storage or indexing.

Practical considerations include clock precision (seconds, milliseconds, or finer), leap seconds, calendar reform issues, and endianness when exchanging binary-encoded dates across platforms. Good practice emphasizes unambiguous, well-documented representations and explicit time-zone handling to ensure portability and correct temporal arithmetic.