About Today Time Date
Today Time Date provides free online clocks, date calculators, time zone converters, and calendar references. Each tool includes calculation rules, examples, and relevant sources.
Online clocks, date calculators and calendar references
Today Time Date brings clocks, calendar references, and date calculators together. You might be finding a meeting time for colleagues on different continents, reading a day-of-year code on a label, checking a deadline, or debugging a timestamp. Each tool is designed around one of those practical questions.
The site has four parts. Today’s date and the current time pages show the present moment in every common format, from ISO 8601 to the Hebrew and Islamic calendars. The world clock, time zone references, and city pages answer “what time is it there?” with sunrise and sunset times, clock-change dates, and working-hour overlaps. The calculators handle date arithmetic, ages, business days, and countdowns. The calendar section and guides explain the rules behind all of it.
Calculation rules and worked examples
Months have different lengths. Standard time and local time are not always the same. A date range can include or exclude its first day. Our explanations make these choices visible, with worked examples you can check yourself. When a calculation is an approximation, such as the simple lunar-cycle model on the moon phase page, we say so and point to a more precise source.
Where the numbers come from
We rely on published standards and public data rather than our own conventions:
- Time zones and daylight saving: the IANA time zone database, as shipped in your browser and in our build.
- Date and week formats: ISO 8601 for week numbers, ordinal dates, and timestamps; RFC 3339 for internet date-time strings.
- Sun and moon: the standard sunrise equation for sun times, and Jean Meeus’s Astronomical Algorithms for new and full moons.
- Other calendars: the Unicode CLDR calendar data built into modern browsers.
- US federal holidays: the observance rules published by the US Office of Personnel Management.
The methodology page documents each method, its accuracy, and a reference you can compare against.
How the tools work
Clocks read your device time. Date calculations and conversions run in your browser, and regional times use the time-zone rules supplied by your browser and operating system. You do not need an account to use the tools, and the dates you type, including birthdays, are not sent to a server. Read the privacy policy for information about analytics.
Keeping pages current
Time rules change more often than people expect. In 2026 alone, British Columbia moved to permanent daylight time and Morocco returned to GMT. When a government announces a change, we update the affected city and time-zone pages, cite the announcement, and note that devices with older time-zone data may still show the previous rule. Pages that list clock changes, holidays, or calendars state the years they cover, so you can see at a glance whether a figure applies to your date.
What this site does not do
We do not claim atomic-clock precision: the live clocks are only as accurate as your device. We do not list every local holiday, school calendar, or employer closure; business-day counts use weekends and, optionally, US federal holidays. Religious dates that depend on a moon sighting can differ from the calculated date by a day. Where a limit like this affects a result, the tool page says so next to the result.
Report a calculation or content error
If a result looks wrong, the most useful report includes the page address, the inputs, your device time zone, and the result you expected. For an explanation that needs correction, include the sentence and a supporting source if you have one. The contact page explains how to get in touch. Confirmed errors are corrected on the page itself.