Date & Time Tools

ArrayKit's date and time tools cover everything from keeping time to converting it. Run an Online Stopwatch with laps and splits, a Countdown Timer with an alarm, a Pomodoro Timer with focus and break cycles, an Interval Timer for Tabata and HIIT, or an Alarm Clock with snooze, and count down to any date with Countdown to Date. Timers read the clock rather than counting ticks, so a tab in the background stays accurate. For development and ops there is the Unix Timestamp Converter, a World Clock and Time Zone Converter, a Cron Expression Generator and Explainer, strftime and ISO duration helpers, and a UUID Generator. Calculators handle age, date differences, business days, week numbers, time cards, sunrise and sunset. Everything runs in your browser and nothing you enter is uploaded.

  • Unix Timestamp Converter — Convert between Unix timestamps and human dates (local + UTC).
  • UUID Generator — Generate up to 1,000 UUIDs at once: random v4, time-ordered v7 or the NIL UUID.
  • Cron Explainer — Explain a cron expression and preview its next run times.
  • World Clock & Time Zone Converter — Compare times across cities on an aligned 24-hour grid and plan meetings — right in your browser.
  • Cron Expression Generator — Visually build a cron expression with live preview, a plain-English summary and next run times.
  • Date Duration Calculator — Calculate the duration between two dates in years, months, weeks, days and business days.
  • Age Calculator — Calculate exact age in years, months and days as of any date, plus totals in weeks, days, hours and next birthday.
  • Duration Converter — Convert a duration between seconds, minutes, hours, days, HH:MM:SS and human formats.
  • Business Days Calculator — Add or subtract working days from a date, or count business days between two dates.
  • Date Calculator — Add or subtract years, months, weeks and days from a date to find the resulting date.
  • Time Duration Calculator — Calculate the hours and minutes between two times of day, even across midnight.
  • ISO Week Number Calculator — Find the ISO-8601 week number for any date, and the date range for a given week.
  • strftime Date Formatter — Format a date with strftime tokens (%Y, %m, %d…) and preview the output live.
  • Relative Time Formatter — Turn a date into a human "time ago" phrase, or humanize a duration.
  • Time Calculator — Add or subtract times and durations, and sum multiple time spans.
  • Time Card Calculator — Total daily and weekly work hours from clock-in/out times minus breaks.
  • Day of the Week Calculator — Find the day of the week for any date, past or future.
  • Sunrise & Sunset Calculator — Sunrise, sunset, solar noon, twilight and golden hour for any date and location.
  • Moon Phase Calculator — Moon phase, illumination and age for any date, with a full-month phase calendar.
  • ISO 8601 Duration Converter — Read and write ISO 8601 durations like PT1H30M, in seconds and plain English.
  • ICS Calendar File Generator — Build an .ics invite with reminders, repeats, attendees and a time zone.
  • Julian Date Converter — Convert calendar dates to Julian Day, MJD and the YYDDD ordinal form.
  • Fiscal Quarter Calculator — Find the fiscal quarter and year for any date, on any financial calendar.
  • Stopwatch — A stopwatch with laps, splits and CSV export that keeps true time in a background tab.
  • Countdown Timer — Set hours, minutes and seconds and get an alarm when time is up — presets, full screen and a share link.
  • Pomodoro Timer — Focus and break cycles with long breaks, session counts and a local daily tally.
  • Alarm Clock — Set one or more alarms with labels, repeat days and snooze — rings while this tab stays open.
  • Interval Timer — Work, rest, rounds and sets with beeps — Tabata, HIIT, EMOM and boxing presets.
  • Countdown to a Date — Live days, hours, minutes and seconds until any date, with holiday shortcuts and a shareable link.

Guides

  • Date Calculations, Explained: Counting and Adding Days — How to count the days between two dates, add days, weeks or months to a date, and why calculators disagree: inclusive counts, month ends and leap years.
  • How Exact Age Is Calculated — How to calculate exact age in years, months and days: the borrow method, 29 February birthdays, total days and weeks, and why calculators differ by a day.
  • Cron Expressions, Explained — Crontab syntax explained: the five cron fields, special characters, common schedules, the day-of-month or day-of-week rule, @daily shortcuts and time zones.
  • Unix Timestamps and Epoch Time, Explained — What a Unix timestamp is, why epoch time ignores leap seconds, how to tell seconds from milliseconds, converting in JS, Python and SQL, and the 2038 problem.
  • Time Zones, UTC and Daylight Saving, Explained — UTC vs GMT, offsets such as +05:30 and +05:45, IANA zone names, why EST and IST are ambiguous, daylight saving shifts, and using a time zone converter well.
  • UUIDs, Explained: v4, v7 and GUIDs — What a UUID is, how the 8-4-4-4-12 format works, UUID v4 vs v7 and the other versions, how unlikely a v4 collision is, and how UUIDs affect database indexes.
  • The Pomodoro Technique, Explained — How the Pomodoro Technique works: the 25-minute focus session, the 5-minute break, the long break after four, popular variations like 50/10, and tips that help.

Frequently asked questions

Which timers and clocks does ArrayKit have?
An online stopwatch with laps, a countdown timer, a Pomodoro timer, an alarm clock, an interval timer for workouts and a countdown to any date, alongside a world clock for comparing time zones. Each runs in your browser and can go full screen.
Will a timer or alarm still go off if I switch to another tab?
Yes while the page stays open: timers measure real elapsed time from the system clock, so a throttled background tab still shows the right time and sounds when it is due. A closed or sleeping tab cannot ring, so keep the tab open and the volume up.
Which cron tool should I use — the Generator or the Explainer?
Use the Cron Expression Generator to build a schedule by picking each field, with a plain-English summary and next run times. Use the Cron Explainer to decode an expression you already have and preview when it will fire.
Can these tools handle time zones and daylight saving time?
Yes. The World Clock and Time Zone Converter aligns cities on a shared 24-hour grid and applies daylight saving rules from your browser's built-in time zone data, and the countdown to a date can be set in your local time or a chosen zone.
Are my dates, schedules and timer settings uploaded anywhere?
No. Every tool processes what you enter on your own device. Timer presets, alarms and Pomodoro history are kept in your browser's local storage so they survive a reload, and you can clear them at any time.
Who are the date and time tools built for?
Developers, DevOps engineers and testers debugging logs, APIs and schedulers, as well as students, athletes and anyone who needs a reliable timer, a quick date calculation or a shareable countdown.