Typedate

Typedate is a concept in software development referring to a strongly typed representation of a calendar date, designed to prevent common errors that arise when dates are handled as strings or loosely-typed data. In a typedate system, a date value encodes year, month, and day in a dedicated type, with invariant validation that rejects invalid dates (for example, February 30) at construction time.

Key characteristics of typedate include immutability, explicit constructors or factory functions, and a rich interface for comparison, normalization, and arithmetic operations such as adding or subtracting days. Parsing from and formatting to textual representations is supported through well-defined patterns to minimize locale and format confusion. Many designs also separate date (the calendar day) from time of day and timezone, providing a composition of types such as Date, Time, Timezone, and DateTime.

In practice, typedates appear in languages with strong type systems or in libraries that aim to replace raw date strings with a dedicated date type. They help catch errors earlier, improve API clarity, and simplify reasoning about date-related logic. Challenges include interoperability with existing string-based data, potential learning curves, and the need for consistent formatting and timezone handling across an application.

See also: date, time, calendar, Temporal API, date library.