Why Hijri dates can differ by one day
The civil calculation and local moon sighting can produce a one-day difference. For official religious dates, follow the authority in your country.
Guides and Explanations
Short, original guides explaining dates, calendars, calculations, and privacy.
How ISO week numbers work
ISO weeks start on Monday. Week 1 is the week containing the first Thursday of the year, which can place early January dates in the previous ISO year.
Why local processing protects privacy
A browser-based tool can calculate age, count words, or generate passwords without sending the entered value to a server.