Time Converter Calculator

Introduction

This Time Converter Calculator helps you change one kind of time into another. You can turn minutes into hours, days into weeks, or seconds into years. Just type a number, pick your units, and get the answer right away.

The tool does more than unit math. You can convert times between world time zones, change a Unix timestamp into a real date, find the time between two dates, add or subtract time from a date, and switch between 12-hour and 24-hour (military) time. There is also a live world clock so you can see the current time in many cities at once.

Each answer comes with clear steps, charts, and copy buttons, so you can check the math and use the result anywhere. It works for school work, travel plans, work shifts, meetings across countries, and coding tasks.

How to use our Time Converter Calculator

Pick a tab, type in your time value, date, or time zone, and the calculator shows the converted answer right away, plus step-by-step math, charts, and copy buttons.

Unit Converter tab

Value: Type the number of time units you want to convert, like 90. Decimals work too.

From unit: Choose the unit your number is in now, such as minutes or days.

To unit: Choose the unit you want the answer in, such as hours. This is your main result.

Swap From / To: Click this to flip the two units and convert the other way.

Decimal value and unit: Enter a decimal time, like 7.25, and pick decimal hours, days, or minutes to see it as clock time.

Clock time boxes: Type days, hours, minutes, and seconds to turn clock time into a decimal number.

Time Zones tab

Date: Pick the date of the time you want to convert.

Time input format: Choose 12-hour or 24-hour so the time boxes match how you write time.

Time: Enter the hour and minute, and pick AM or PM if you chose 12-hour.

Source time zone: Pick the city or zone where that time comes from.

Destination time zones: Pick up to 10 zones you want the time changed into. Use Add Destination for more.

Unix / Epoch tab

Unix timestamp: Paste the timestamp number to turn it into a real date and time.

Timestamp unit: Choose seconds, milliseconds, or microseconds, or leave it on auto-detect.

Show also in this time zone: Pick one extra zone to see the date in your local area.

Date and time (right side): Enter a date and a 24-hour time to get its Unix timestamp.

Time zone of that date & time: Pick the zone that date and time belongs to.

Duration tab

Start date, time, and zone: Enter when the time period begins.

End date, time, and zone: Enter when it ends, to get the time between the two.

Base date, time, and zone: On the Add / Subtract screen, enter the date you start from.

Operation: Choose add or subtract.

Years, months, weeks, days, hours, minutes, seconds: Type how much time to add or take away.

12 / 24 Hour tab

Hour, minute, second, AM/PM: Enter a 12-hour clock time to get the 24-hour (military) time.

24-hour hour, minute, second: Enter a military time to get the 12-hour time with AM or PM.

World Clock tab

Time zone: Pick a zone and click Add Clock to show its live time. You can show up to 12 clocks.

Time Conversion Explained

Time conversion means changing one way of writing time into another. You might turn 90 minutes into 1.5 hours, change 2:35 PM into 14:35, or find out what time it is in Tokyo when it is noon in New York. All of these use simple math and a few fixed rules.

How Time Units Fit Together

The second is the base unit of time. Every other unit is built from it. The easiest way to convert is to change your number into seconds first, then divide by the unit you want.

1 minute = 60 seconds
1 hour = 60 minutes = 3,600 seconds
1 day = 24 hours = 86,400 seconds
1 week = 7 days = 604,800 seconds
1 month (average) = 30.4375 days
1 year (average) = 365.25 days = 31,557,600 seconds

Months and years do not have one exact length. Months run from 28 to 31 days, and leap years add a day. So long conversions use average values, and calendar math (like "1 month after January 31") uses real dates instead.

Time Zones and UTC

The world is split into time zones. Each zone is set as a number of hours ahead of or behind UTC (Coordinated Universal Time), the world's time standard. For example, UTC−5 is five hours behind UTC, and UTC+9 is nine hours ahead.

To convert between two zones, find the gap between their offsets and add or subtract it. If the new time passes midnight, the date changes too, which is why a call at 9:00 AM Monday in Los Angeles happens at 2:00 AM Tuesday in London.

Daylight Saving Time

Many places move their clocks forward one hour in spring and back one hour in fall. This changes their UTC offset for part of the year, and countries switch on different dates. Because of this, the gap between two cities is not always the same all year long.

12-Hour and 24-Hour Clocks

The 12-hour clock repeats 1 to 12 twice a day and uses AM (midnight to noon) and PM (noon to midnight). The 24-hour clock, often called military time, counts 00:00 to 23:59, so there is no confusion.

Midnight 12:00 AM = 00:00
9:30 AM = 09:30
Noon 12:00 PM = 12:00
2:35 PM = 14:35 (add 12 to any PM hour except 12)
11:45 PM = 23:45

Unix Timestamps

Computers often store time as a single number: the count of seconds since January 1, 1970 at 00:00:00 UTC. This is called Unix time or epoch time. Some systems count milliseconds or microseconds instead, which makes the number much longer. Timestamps have no time zone, so the same number points to the same instant everywhere on Earth.

Durations and Decimal Time

A duration is the amount of time between two moments. Subtract the start from the end to get it, then show it in the units you need. Time sheets and payroll often use decimal hours, where the minutes become a fraction of an hour: 15 minutes is 0.25 hours, 30 minutes is 0.5 hours, and 45 minutes is 0.75 hours. So 7 hours 15 minutes is written as 7.25 hours.

Where Time Conversion Is Used

Setting up meetings and video calls across countries
Booking flights and reading arrival times
Filling in work hours and billing clients, along with overtime and PTO tracking
Reading log files and database dates in code, and estimating download times
Cooking, workouts, science labs, and sports timing such as running pace
Counting down to deadlines
Working out ages and anniversaries

Formulas used

Convert a value between two time units (via seconds)

t_{\text{target}} = \frac{v \times s_{\text{from}}}{s_{\text{to}}}

UTC offset of a time zone (minutes)

\Delta_{\text{tz}} = \frac{t_{\text{wall as UTC}} - t_{\text{instant}}}{60000}

Wall-clock time to absolute instant (epoch ms)

t = \text{UTC}(y,m,d,h,mi,s) - \Delta_{\text{tz}} \times 60000

Elapsed duration between two date-times

\Delta t = t_2 - t_1 \quad\Rightarrow\quad \text{sec} = \frac{|\Delta t|}{1000},\ \ \text{hr} = \frac{\text{sec}}{3600},\ \ \text{days} = \frac{\text{sec}}{86400}

Decimal time to days, hours, minutes, seconds

d = \left\lfloor \frac{T}{86400} \right\rfloor,\quad h = \left\lfloor \frac{T - 86400d}{3600} \right\rfloor,\quad mi = \left\lfloor \frac{T - 86400d - 3600h}{60} \right\rfloor,\quad s = T - 86400d - 3600h - 60mi

Unix timestamp to and from seconds / milliseconds / microseconds

t_{\text{ms}} = t_s \times 1000 = t_{\mu s} \div 1000,\qquad t_s = \left\lfloor \frac{t_{\text{ms}}}{1000} \right\rfloor

12-hour to 24-hour clock conversion

H_{24} = (h_{12} \bmod 12) + 12 \cdot [\text{PM}],\qquad h_{12} = ((H_{24} + 11) \bmod 12) + 1

Seconds and decimal hours since midnight

\text{sec} = 3600H + 60M + S,\qquad \text{hr}_{\text{dec}} = H + \frac{M}{60} + \frac{S}{3600}

Frequently asked questions

Why is my month result a little different from another calculator?

The Unit Converter tab uses an average month of 30.4375 days. Other tools may use 30 or 31 days.

If you need exact months, switch to the Duration tab and enter two real dates. That method counts the true days in each month.

Why does the total days number not match the years, months, and days answer?

The Duration tab shows two things. The calendar breakdown counts real months, which vary in length. The total days number is the raw gap divided by 24 hours.

Both are correct. Use the breakdown for calendars and the totals for math.

Why does January 31 plus 1 month give February 28?

February has no 31st day, so the date is clamped to the last day of the month. In a leap year you get February 29.

This is the standard rule used by calendars and software.

Why did the date change when I converted a time zone?

Some zones are so far apart that the converted time lands on the day before or after. The Day shift column tells you if it is the same day, plus one day, or minus one day.

This is normal for calls between places like the United States and Asia.

How does auto-detect know if my timestamp is seconds or milliseconds?

It looks at how long the number is. Ten-digit numbers are read as seconds, thirteen-digit numbers as milliseconds, and very long numbers as microseconds.

If the date looks wrong, pick the unit yourself from the dropdown.

Do Unix timestamps have a time zone?

No. A timestamp is one number counting from January 1, 1970 UTC, so it means the same instant everywhere.

The time zone only matters when you turn it into a readable date. That is why the tool shows UTC, your local time, and a zone you choose.

What happens if my end date is before my start date?

The Duration tab still works. It shows the result as a negative value and warns you that the start comes after the end.

Swap the two dates if you want a positive answer.

How do I convert 12:00 AM and 12:00 PM correctly?

12:00 AM is midnight and becomes 00:00. 12:00 PM is noon and stays 12:00.

Only these two hours break the add-12 rule, which is why the reference table lists every hour.

Why does my time card show 7.25 hours instead of 7 hours 15 minutes?

Payroll systems use decimal hours. Minutes become a fraction of an hour, so 15 minutes is 0.25.

Type the clock time in the Decimal Time section and the tool gives you the decimal number to enter.

Is the world clock live and accurate?

Yes. Each clock updates every second and uses your device's clock plus official time zone rules.

If your device clock is wrong, every clock will be off by the same amount.

Are my dates and times saved anywhere?

No. All math runs in your browser, and nothing is sent to a server or stored.

Refreshing the page resets the tool to its default values.

Can I use very small or very large numbers?

Yes. Nanoseconds up to millennia are supported, and decimals work too.

Very big or very small results are shown in scientific notation, like 1.5 × 10^12, so they stay readable.