Olutil – Online Utilities

Free Online Time Tools

Olutil stands for Online Utilities — a growing suite of privacy-first, browser-native web tools. This sub-site brings you a complete suite of time utilities that run entirely in your browser: Unix timestamp converters, date difference calculators, timezone converters, world clocks, countdown timers and more, all in one place. 100% Local Processing

Timestamp Converters

Date Calculators

Date Calculator

Calculate the exact difference between two dates in days, weeks, months and years. Shows the calendar difference and total hour...

Date Difference Calculator

Difference between two dates with inclusive day counts, working days, non-working days, excluded public holidays and total week...

Business Days Calculator

Count working days between two dates. Customisable rest days, public holiday exclusions, calendar days and weekly workdays. Fre...

Add Days to Date

Add or subtract days, weeks, months, years, hours, minutes and seconds from any date. Shows the result in ISO 8601, RFC 2822 an...

Day of the Week Calculator

Find the weekday of any date, with ISO weekday number, day of year, ISO week and the first weekday of the month. Free online da...

Week Number Calculator

Find the ISO 8601 week number, ISO week date, US week number, day of year, quarter and leap year status of any date. Free onlin...

Leap Year Checker

Check if any year is a leap year under the Gregorian rules, with the century exception explained. Shows day counts and nearby l...

Age Calculator

Calculate exact age in years, months and days from a birth date, with total months, weeks, days and hours, plus your next birth...

Next Birthday Calculator

Live countdown to your next birthday. Shows days remaining, the date, your current age and today clock, updating every second. ...

Date Range Generator

List every date between two dates with a custom step: daily, weekly, monthly or yearly. Shows count and calendar span. Free onl...

Random Date Generator

Generate random dates between two bounds in five formats: YYYY-MM-DD, US or European order, ISO with time, or Unix seconds. Fre...

Time Zone Tools

Timers & Countdowns

Formatting & Converters

Date Formatter

Format any date with your own pattern. Tokens for year, month, day, week, day of year, weekday and offset. Presets included, ru...

Seconds to HH:MM:SS

Convert seconds to HH:MM:SS with days and hours broken out for long durations. Handles fractions and totals. Free online second...

HH:MM:SS to Seconds

Convert a HH:MM:SS or H:MM:SS duration string to total seconds, minutes and hours. Handles hours above 24. Free online time con...

Time Unit Converter

Convert time between seconds, minutes, hours, days, weeks, months and years. Shows every unit in one conversion. Free online ti...

ISO 8601 Duration Converter

Parse ISO 8601 durations like P1Y2M3DT4H5M6S into total seconds, minutes, hours and days, or build an ISO duration from a plain...

Excel Date Converter

Convert between Excel serial numbers and real dates. Handles the 1900 leap year bug, the 1904 Mac system, and time fractions in...

Julian Date Converter

Convert between Julian Date, Modified Julian Date and normal calendar dates. Astronomical continuous day count, accurate to the...

GPS Time Converter

Convert Unix time to GPS time, GPS week number, NTP 64 bit timestamp and TAI. Includes the 37 second leap offset and NTP hex fr...

HTTP Date Formatter

Format HTTP date headers like Sun, 06 Nov 1994 08:49:37 GMT. Convert between HTTP dates, ISO 8601, Unix timestamps and local ti...

Cookie Expiry Calculator

Calculate cookie expiration from a session length or an exact date. Get the Expires header, Max-Age seconds and a ready Set-Coo...

Calendars & Clocks

Cron & Scheduling

Work Time Tools

How It Works

Every tool on this site runs as a self-contained page in your browser. There is no backend server, no account and no upload: you type or paste a value, the page computes the result on your own device and displays it instantly.

Pick a tool from the grid below, make your selection or paste your data, and press the convert or calculate button. The result appears immediately with the values you need, ready to copy.

Frequently Asked Questions

Are all the time tools really free?

Yes. Every tool on time.olutil.com is free to use, runs entirely in your browser and needs no account or sign-up of any kind.

Do you upload or store the dates I enter?

No. All processing happens locally in your browser. Your dates, timestamps and timezones are never sent to any server.

What is a Unix timestamp?

A Unix timestamp counts the seconds since 1 January 1970 00:00:00 UTC. This tool converts between those numbers and normal dates.

Do these timezone tools keep daylight saving time correct?

Yes. Offsets are computed from your browser built-in timezone database, so daylight saving transitions are handled automatically.

Can I use these tools on my phone?

Absolutely. The whole site is responsive and works on any screen, and because every tool is self-contained you can keep it open as a reference.

All Tools