datehandling

Date handling refers to operations on calendar dates and times within software applications. It encompasses representation, storage, parsing, formatting, comparison, arithmetic, and localization. Core types include date (year, month, day), time (hour, minute, second), datetime or timestamp (combination), and durations/intervals. One challenge is time zones and daylight saving time, since same instant may appear differently in local time. Best practice is to store or transmit times in a standard reference such as Coordinated Universal Time (UTC) or an ISO 8601 string, and convert to user local time for display. ISO 8601 is widely used for exchange, e.g., 2025-12-31T23:59:59Z. Time zone databases (IANA TZ) underpin accurate conversions.

Common operations include parsing user input, validating dates, formatting according to locale, comparing timestamps, and performing arithmetic (adding days, difference in days, duration). Leap years (Gregorian: divisible by 4, not by 100 unless by 400) and leap seconds can affect calculations. Leap seconds are inserted occasionally, rarely affecting time arithmetic; some systems ignore them and treat time as continuous.

Localization considerations involve format order (year-month-day vs day-month-year), names of months, and first day of week. Libraries provide robust date handling and often separate date and time concepts, offering immutable types and timezone-aware objects. Examples include standard libraries in major languages and specialized libraries for precise calendrical calculations.

Common pitfalls include ambiguous local times during DST transitions, invalid dates from user input, and forgetting to normalize to UTC before storage. A disciplined approach uses a canonical internal representation, clear input validation, and locale-aware formatting at presentation time.