date-operations

Use the date-fns library for all date operations in TypeScript rather than writing custom helpers or manual calculations. It provides tested functions for formatting, arithmetic, parsing, and comparison with strong TypeScript support.

date-fns is the recommended choice for date formatting and manipulation in TypeScript. It offers modular, tree-shakeable functions like format, addDays, and differenceInDays, avoiding the pitfalls of hand-rolled date logic.

date-fns is preferable to custom helpers because it is maintained, tested across edge cases like month boundaries and leap years, and documented. Custom helpers often contain subtle bugs and duplicate functionality the library already provides.

Consult the official date-fns documentation at https://date-fns.org/docs/Getting-Started when function behavior is unclear. The docs detail each function's arguments, return values, and edge-case handling.

Avoid manual date calculations whenever a library function exists, since native Date arithmetic mishandles month lengths, daylight saving transitions, and timezone offsets. Use date-fns functions for any non-trivial date logic.