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Time Calculator

Add or subtract time durations, and convert between US time zones.

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Duration Calculator

Add or subtract hours, minutes, and seconds.

First time duration. Enter hours, minutes (0–59), and seconds (0–59).

Second time duration to add or subtract from the first.

Result
4h 5m 45s
= 14,745 seconds total

Time Zone Converter

Convert a time between US time zones.

Enter the time you want to convert. Use 24-hour format (e.g. 14:00 = 2:00 PM).

Select the time zone the input time is in. The table below shows the equivalent time in all other US zones.

Equivalent Times
Eastern (ET) —
Central (CT) —
Mountain (MT) —
Pacific (PT) —
Alaska (AKT) —
Hawaii (HST) —
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Frequently Asked Questions

How do I add time durations together?
To add time durations, add the hours, minutes, and seconds separately, then carry over: if seconds exceed 59, subtract 60 from seconds and add 1 to minutes; if minutes exceed 59, subtract 60 from minutes and add 1 to hours. For example, 2h 45m + 1h 30m = 3h 75m = 4h 15m. Our calculator handles this automatically, so you can enter any number of hours, minutes, and seconds and get the correct summed result instantly.
How do I subtract time?
Time subtraction works similarly to addition but with borrowing. If the seconds or minutes being subtracted are larger than the current seconds or minutes, you borrow from the next larger unit. For example, 3h 10m − 1h 45m: first borrow 1 hour (making it 2h 70m), then subtract to get 1h 25m. The calculator handles all the borrowing logic automatically so you don't need to do the mental gymnastics.
What are the US time zones?
The continental United States has four main time zones: Eastern Time (ET, UTC-5/UTC-4 with DST), Central Time (CT, UTC-6/UTC-5), Mountain Time (MT, UTC-7/UTC-6), and Pacific Time (PT, UTC-8/UTC-7). Alaska uses Alaska Time (AKT, UTC-9/UTC-8) and Hawaii uses Hawaii-Aleutian Standard Time (HAST, UTC-10, no DST). During Daylight Saving Time (second Sunday in March to first Sunday in November), most states move clocks forward one hour.
What is Daylight Saving Time and when does it change?
Daylight Saving Time (DST) is the practice of advancing clocks by one hour during summer months to extend evening daylight. In the United States, clocks "spring forward" at 2:00 AM on the second Sunday of March and "fall back" at 2:00 AM on the first Sunday of November. Hawaii and most of Arizona (except the Navajo Nation) do not observe DST. Several other US territories also do not observe DST.
How many hours difference is Eastern Time from Pacific Time?
Eastern Time (ET) is 3 hours ahead of Pacific Time (PT) year-round. When it's 12:00 PM (noon) in New York (Eastern), it's 9:00 AM in Los Angeles (Pacific). When it's 9:00 PM in Los Angeles, it's midnight (12:00 AM next day) in New York. This difference remains constant because both zones observe Daylight Saving Time and shift simultaneously.
How do I convert between time zones for a meeting?
To schedule a cross-timezone meeting, determine the current time in your timezone, then add or subtract the offset between your zone and the target zone. Eastern is +3 from Pacific, +2 from Mountain, +1 from Central. So a 2:00 PM Eastern meeting is 11:00 AM Pacific, 12:00 PM Mountain, 1:00 PM Central. Use the time zone converter below to check any time conversion instantly without mental math.
How many hours are in a week or month?
A week has exactly 168 hours (24 hours × 7 days). A month has approximately 720–744 hours depending on the month (28–31 days × 24 hours). A year has 8,760 hours in a standard year and 8,784 hours in a leap year. A work month typically contains about 160–173 work hours based on 40-hour weeks, accounting for varying numbers of weekdays per month.
What is the difference between duration and clock time?
Duration is the length of a time interval (e.g., 2 hours and 30 minutes). Clock time is a specific point in the day (e.g., 3:45 PM). The time duration calculator adds or subtracts durations from each other. If you want to find what clock time it will be 2h 30m after 1:15 PM, that's a different calculation (start time + duration = end time). Both types are useful in scheduling, work time tracking, and event planning.

US Time Zones: Why Time Is More Complicated Than You Think

The continental United States spans four main time zones: Eastern, Central, Mountain, and Pacific. When it's noon in New York, it's 11am in Chicago, 10am in Denver, and 9am in Los Angeles. Alaska adds a fifth time zone, and Hawaii sits in a sixth.

Daylight Saving Time complicates things further. Clocks move forward one hour in March and back one hour in November. This means Eastern time is UTC-5 in winter (EST) and UTC-4 in summer (EDT). Arizona — except for the Navajo Nation — does not observe Daylight Saving Time. Neither does Hawaii. This creates the odd situation where Arizona and California share the same clock in summer but are an hour apart in winter.

For remote workers and distributed teams, these differences have real scheduling consequences. A 9am meeting in New York is 6am in Los Angeles — technically workable but early. The same meeting is 10:30pm in India (India Standard Time is UTC+5:30, with no daylight saving adjustment). This is why most US-India remote teams find the 8–10am Eastern window to be the only truly workable overlap — it hits late afternoon in India rather than late evening.

Duration calculations break in a specific and annoying way when they cross midnight. A shift from 10:30pm to 6:15am is 7 hours and 45 minutes, but simple subtraction gives a negative number. The calculator handles this by detecting when the end time is earlier than the start time and adding 24 hours before subtracting.

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About This Time Calculator

The duration calculator lets you add or subtract two time durations expressed in hours, minutes, and seconds. It automatically handles carrying and borrowing across units—so if your addition results in 75 minutes, it correctly converts to 1 hour and 15 minutes. This is useful for tracking work hours, workout durations, travel time estimates, or any scenario where you need to combine time intervals.

The time zone converter shows you the equivalent clock time across all six major US time zones simultaneously. Enter a time and your source time zone, and all conversions update instantly. The converter uses your browser's built-in internationalization API for accurate timezone offsets including Daylight Saving Time adjustments—so results are always correct for the current date.