Date & time

Calculate exact age from a birth date with optional as-of date. Fully client-side — no account, uploads, or remote storage.

Measure gaps between two calendar dates including leap years. Fully client-side — no account, uploads, or remote storage.

Find elapsed time between two clocks, optionally across midnight. Fully client-side — no account, uploads, or remote storage.

Convert epoch seconds or milliseconds to ISO dates and back with timezone context. Fully client-side — no account, uploads, or remote storage.

Convert a local datetime between IANA zones with DST rules explained. Fully client-side — no account, uploads, or remote storage.