Idiot Date Tools is a single-purpose toolbox built around one thing: calendar and date calculations. Every tool on this site — from a simple age calculator to a multi-timezone meeting planner — solves one specific, narrow date-related problem, runs entirely inside your browser, and gives you a straight answer without accounts, popups over the calculator, or unnecessary steps.
Most "everything calculator" sites bury the tool you actually want under dozens of unrelated categories. We went the other way: this site does date and calendar math, and nothing else, so every tool is easy to find, consistent to use, and built by people who actually understand the edge cases — leap years, timezone daylight saving shifts, ISO week numbering, lunar calendar drift — that trip up naive date calculations.
Every calculator runs as client-side JavaScript directly in your browser. Nothing you type into a date field, birth date, or timestamp is ever transmitted to a server or stored anywhere. Calculations happen instantly and privately on your own device.
We aim for calculation accuracy across all standard date and calendar rules, including leap years, daylight saving transitions and the ISO-8601 week standard. If you ever spot a calculation that looks wrong, please get in touch via the Contact page.