Time tools
18 tools
Tools for time: world clock, Unix timestamp conversion, and more.
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Age calculator — from birthday to years, zodiac & day count
Enter a birth date and a reference date to get the full age in years, days lived, Eastern zodiac (12 animals), and Western zodiac. Change the reference date to compute the age at any past or future point. Everything runs inside your browser — your birthday never leaves the page.
timecalculator
Anniversary counter — years/months/days/hours since a date
Type a start date (relationship, wedding, business launch, fan-club anniversary) and instantly see the elapsed time as 『Y years M months D days』, weeks, days, hours, minutes, and seconds. Upcoming milestones (100, 200, 1000 days, 1/5/10 year marks…) are computed with their own countdowns. Updates every second; copy any value in one click. Where age-calc is birthday-specific, this tool fits any anniversary. Everything runs in your browser.
timecalculator
China business-day calculator — Spring Festival, National Day, 调休 makeup days
Compute the date that is N business days before or after a given date, skipping Chinese public holidays (New Year, Spring Festival, Qingming, Labour Day, Dragon Boat, Mid-Autumn, National Day) and weekends. Honours 调休 (makeup work-days) — weekends officially designated as working days to bridge long holidays. Data follows the State Council's published 2024 and 2025 schedules; 2026 is an approximation pending official notice. Runs entirely in your browser.
timecalculator
JP business-day calculator — count workdays excluding holidays
Compute the date that is N business days before or after a given date, skipping Japanese national holidays plus weekends. Handles substitute holidays, citizen's holidays, and vernal/autumnal equinoxes (1955-2099). Useful for due dates, settlement dates, and Japan-side delivery scheduling. Runs entirely in your browser.
timejapanesecalculator
US business-day calculator — count workdays excluding federal holidays
Compute the date that is N business days before or after a given date, skipping the 11 US federal holidays (New Year's, MLK Day, Presidents' Day, Memorial Day, Juneteenth, Independence Day, Labor Day, Columbus Day, Veterans Day, Thanksgiving, Christmas) and weekends. Saturday-fall holidays observed Friday and Sunday-fall observed Monday, per federal employee rules. Juneteenth recognised from 2021; MLK Day from 1986. Runs entirely in your browser.
timecalculator
Countdown / count-up timer — time left or elapsed until target date
Real-time display of the remaining time until (countdown) or the elapsed time since (count-up) a target date. Days / hours / minutes / seconds tick every second. Copy the URL to share the current setup (?to=datetime&mode=countdown). Uses your browser's local timezone. Runs entirely in your browser — the target datetime never leaves your device.
time
Countdown Board (multiple events at a glance)
Pin multiple upcoming events (exams, trips, project deadlines, anniversaries, concerts…) onto a single board and watch each remaining time tick down side by side. Each entry takes just a name plus a date-time, and the whole board is auto-saved to your browser's localStorage so it survives reloads. The countdown (DDd HH:MM:SS) updates every second and flips to '—' once the deadline passes. Holds up to 50 entries. Runs entirely in your browser — nothing is uploaded.
calculator
Date difference calculator — days / weeks / months / years
Compute the gap between two dates in days, weeks, business days, a years-months-days breakdown, and (optionally) hours/minutes/seconds. Toggle inclusivity and time-of-day with a checkbox. Everything runs inside your browser.
timediffcalculator
Duration format converter — seconds, mm:ss, hh:mm:ss & 1h30m bulk
Convert durations between three formats: seconds (5400), clock (01:30:00), and human-readable (1h30m). Pick the output format and the input is auto-detected — even mixed formats on different lines. Bulk-converts multi-line input and reports skipped (unparseable) lines. Supports d/h/m/s units (1d = 86400 seconds). Runs entirely in your browser.
timeconversionformat
Interval Timer (HIIT / Tabata work / rest round manager)
A browser-only interval timer for HIIT (High-Intensity Interval Training) and Tabata (20 s work / 10 s rest × 8 rounds). Configure warm-up, work, rest, cool-down and rounds in seconds, with the current phase / remaining time / round progress shown live. Settings autosave to localStorage. Phase transitions trigger short Web Audio beeps (work start = high 880 Hz, rest start = low 440 Hz, finished = chord), and the final 3 seconds add an optional countdown tick. One-click presets: Tabata (20/10 × 8), HIIT 30/30, HIIT 45/15, HIIT 40/20. Uses `performance.now()` deltas so transitions stay accurate in throttled background tabs. Timer logic and audio all run inside your browser — nothing is uploaded.
timecalculatorgenerate
ISO 8601 week number ⇔ date — find week-of-year & week start
Convert between ISO 8601 week numbers (e.g. 2026-W21-6) and calendar dates (e.g. 2026-05-23). Pick the output format with a mode toggle. Week-only input (2026-W21) is parsed as the Monday of that week. Follows ISO rules: W01 is the week containing 4 Jan, weeks start on Monday, and year-boundary cases (2024-12-30 = 2025-W01-1) are handled correctly. Runs entirely in your browser.
timecalculator
Moon Phase & Moon Age Calculator
Calculate the moon age, phase (new / first quarter / full / last quarter) and illuminated fraction for any date and time, shown as a moon diagram. Also finds the next new, first-quarter, full, and last-quarter moments. A mean synodic-month approximation that runs entirely in your browser.
timecalculator
Pomodoro Timer (25 / 5 / long-break cycle)
A browser-only Pomodoro timer for focused work cycles: 25 minutes work + 5 minutes short break, then a 15–30 minute long break every fourth pomodoro. Customise work / short-break / long-break minutes, number of cycles and the audio chime — settings autosave to localStorage. Phase-end chimes are synthesised with the Web Audio API (descending for work-end, ascending for break-end, a C-major chord for set-end). Uses `performance.now()` deltas so transitions stay accurate even in throttled background tabs. Timer logic, settings and audio all run inside your browser — nothing is uploaded.
calculatorgenerate
Stopwatch — lap timing with millisecond precision
A simple in-browser stopwatch with 0.01s precision and lap (split) recording. Keeps running as long as the tab stays open, and lets you export laps as CSV. While countdown counts toward a target time, this measures elapsed time from now. There is no data input — everything stays in your browser.
time
Sunrise & Sunset Calculator
Enter a latitude, longitude and date to compute sunrise, sunset, solar noon, day length and the sun's noon altitude for that location. Also finds civil, nautical and astronomical twilight (dawn and dusk). Includes presets for major cities. A NOAA-style astronomical approximation that runs entirely in your browser.
timecalculator
Date arithmetic — add or subtract years / months / days / hours / minutes
Add or subtract years, months, weeks, days, hours, minutes or seconds from a base date and time. Useful for due-date calculations, contract expirations, scheduling N days ahead or N hours back. Month-end arithmetic follows JavaScript's Date roll-over rules (e.g. Jan 31 + 1 month becomes Feb 28/29). The result shows the new local timestamp, the weekday, a diff summary versus the base and the Unix epoch. Runs entirely in your browser — your input never leaves the device.
timecalculator
Timezone converter — any date/time to multiple cities at once
Pick a date/time and source IANA timezone, then see the equivalent local time in many target timezones at once, with UTC offsets and ±day badges for date rollovers. Handy for cross-border meeting scheduling, deadline translation, and DST-aware comparisons. Runs entirely in your browser via the Intl API.
timeconversion
World clock — real-time current time across major global cities
Show the current time across multiple cities live, side by side. Pin one city's time as the base and the rest update to the matching local time. Cities can be added or removed freely.
time
About this category
Tools for time and dates: a world clock, timezone conversion, Unix timestamp ↔ datetime, day differences, age and duration calculations, business-day arithmetic with Japanese / US / Chinese holiday data, ISO week numbers, moon phase, sunrise and sunset, a stopwatch, countdowns, and more.
Everything is computed locally from your browser's clock and bundled calendar data, so it is fine to use for confidential project deadlines, international meeting planning, observation or shoot scheduling, and similar.
What you can do
- Pre-meeting timezone conversion and a world clock at a glance
- Turn a Unix timestamp from a log into a human-readable datetime
- Compute exact age and elapsed days from a birthday
- Business-day arithmetic that respects JP / US / CN holidays
- Add or subtract dates and show the duration between two points
- Sunrise / sunset and moon-phase calculations for observation or shoots
Category FAQ
- How far ahead does the holiday data go?
- Holidays for the next few years — typical business-planning horizons — are supported. We update as laws change.
- Does timezone conversion handle DST?
- Yes. Conversions use the browser's Intl APIs together with the IANA timezone database, including DST.
- Does Unix-timestamp support cover milliseconds and microseconds?
- Seconds, milliseconds, and microseconds are all accepted as input and detected automatically by digit count.
- How precise are sunrise and sunset?
- We use astronomical libraries that are precise enough for ordinary use. For navigation or precision observation that needs minute-level accuracy, use a dedicated tool.