Every tool on Times & Dates runs calculations directly in your browser. When you enter a date, a city, or a pair of coordinates, that input is processed locally and never sent to a server. Results appear instantly because there is no network roundtrip between your input and the answer.
The math and the data come from the same reference sources used by operating systems and standard libraries. Time zone rules come from the IANA Time Zone Database. Sun and moon positions use the suncalc library, which implements algorithms from the National Renewable Energy Laboratory and Jean Meeus's Astronomical Algorithms. Public holiday listings come from the Nager.Date API. Calendar math follows ISO 8601 and the Gregorian calendar rules.
Every conversion on this site resolves a full IANA zone identifier such as America/New_York or Europe/Berlin rather than a fixed UTC offset. This matters because an identifier encodes the complete DST history and future schedule of a zone, while a fixed offset silently breaks when clocks change. The US and Europe switch on different dates each year, so the gap between New York and London is five hours most of the year but four hours for a few weeks each spring.
When a government changes a time zone rule, IANA publishes a tzdata release, typically three to five per year. The tools pick up the new rules when the site is rebuilt on the updated data. There can be a short window between a government announcement and the data reaching this site, so for time-sensitive decisions it is worth confirming the current offset with an authoritative source.
Sunrise, sunset, twilight, sun position, and day length are computed from your latitude, longitude, and the date, using the solar position algorithms that suncalc implements. Moon phase, moonrise, moonset, and moon distance use the library's lunar position math. Eclipse timing and solstice and equinox dates use the same ephemeris approach described in Meeus's Astronomical Algorithms.
Expect results within a few minutes of the official times for most locations. The calculations assume a flat horizon at sea level and standard atmospheric refraction. Elevation, terrain, and unusual weather can shift the observed time by several minutes either way. For eclipse planning or anything where a few minutes matters, cross-check against NASA or the US Naval Observatory.
Holiday dates come from the Nager.Date API, which aggregates public holidays from government sources for over 100 countries. Many countries observe holidays at the regional level rather than nationwide, and governments occasionally declare or move holidays with little notice. The listing can lag those declarations, so a date shown here should be verified with the official government source before you rely on it for payroll, deadlines, or travel.
The individual holiday detail pages on this site, covering the history and observance of each holiday, are written and reviewed by hand rather than generated from the API feed.
Date calculations follow the Gregorian calendar, including the century-year exception to the leap rule: 1900 was not a leap year, 2000 was. Week numbers use ISO 8601, where week 1 is the week containing the first Thursday of the year, which is why late December dates can belong to week 1 of the following year.
Business-day counts exclude Saturdays and Sundays. Public holidays are only excluded when you select a country, because there is no universal holiday calendar. Time duration results separate calendar days from working days so the difference is explicit rather than assumed.
Time zone conversions are exact for dates the current tzdata covers. Historical offsets before roughly 1970 are less reliable because IANA records for many zones are approximate that far back. Future dates assume the DST rules legislated today; if a country changes its law, future conversions will change with it.
Astronomy results are accurate to within a few minutes for most uses. Holiday data is sourced from an aggregator and can lag official declarations. The tools are for general informational use and are not a substitute for legal, payroll, or aviation-grade references.
Times & Dates is an independent project and is not affiliated with or endorsed by these organizations.
How accurate are the time zone conversions?
They are exact for any date the IANA database covers, because the conversions resolve the full zone rules rather than a guessed offset. The only failure mode is a government changing the rules faster than tzdata ships the update, which is rare and short-lived.
Why do my sunrise times differ from another site by a few minutes?
Different sources assume different values for atmospheric refraction, observer elevation, and horizon height. A difference of a few minutes between reputable sources is normal and does not mean either one is wrong.
How often is the underlying data updated?
IANA releases tzdata three to five times per year as governments change rules. Holiday data updates as Nager.Date ingests new government publications. The site is rebuilt to pick up changes rather than caching them indefinitely.
Can I rely on the holiday dates for payroll or legal deadlines?
Verify them with the relevant government source first. The data comes from a well-maintained aggregator, but regional observances and last-minute declarations are exactly the cases where an aggregator can lag.
Who maintains this methodology?
The same developer who builds the tools, Dandre Noah. If you spot an error in the data or in this page, use the contact page and the report goes to him directly.