Add signed years, months, days, hours, minutes or seconds to an ISO instant.
Type or paste on the left — the result updates as you type.
Calendar operations use UTC. Month and year additions clamp to the last day of the destination month. Negative amounts subtract.
Up to 100,000 UTF-16 units per input and 1,000,000 per result. See the supported formats and examples below.
Tool page updated: 2026-09-27
