Time & Date Now

About & data sources

A reference for time: clocks, zones, calendars, and the Sun and Moon — built to run entirely in your browser with nothing sent to a server.

What this site is

Time & Date Now is a set of time, date and astronomy tools: world clocks, a time zone converter and meeting planner, calendars and date calculators, sunrise and moon data, public holidays, timers and countdowns. Everything is computed on your device. There is no account system, no analytics and no server-side processing.

How the times are computed

Time zone offsets and daylight-saving rules come from the IANA Time Zone Database (tzdata), which your browser ships and exposes through the standard Intl.DateTimeFormat API. tzdata is public domain and is updated several times a year as governments change their rules; your browser vendor delivers those updates. Because the site reads the browser's copy, it does not need to be redeployed when a country changes its DST schedule.

Astronomy

  • Sunrise, sunset and twilight use the standard almanac algorithm with the usual zenith angles (90.833° for rise/set; 96°, 102° and 108° for civil, nautical and astronomical twilight).
  • The Moon uses a truncated series from Jean Meeus's Astronomical Algorithms, accurate to about half a degree — sufficient for rise/set times and phase.
  • Planets use the JPL approximate Keplerian elements valid for 1800–2050.
  • Eclipses follow NASA's Five Millennium Canon of Solar and Lunar Eclipses (public domain).
  • Seasons use published equinox and solstice instants.

Reference data

  • Public holidays are curated by hand for 14 countries for 2026. No reliable free worldwide source exists; substitute days, regional observances and lunar-calendar variance are noted where they apply.
  • Climate normals are approximate long-term monthly averages for orientation, not forecasts.
  • Currency rates are indicative reference values; check a live market feed before transacting.
  • City coordinates and facts (region, population, capital, ISO 3166 and dialing codes) are curated reference values.
  • Leap seconds follow the IERS Bulletin C record.

Accuracy and limits

The astronomical values are approximations suitable for everyday use; they are not intended for navigation or scientific work. Holiday dates for lunar calendars (Islamic, Hindu, Chinese) can differ by a day depending on the observing authority. If you spot an error, please let us know.