Convert a specific date and time between U.S. and world time zones, compare current local times, and plan meetings without manually calculating UTC offsets or daylight-saving changes.
Time Zone Calculator
Pick a mode below. Conversions use your browser's built-in IANA time zone rules for the exact date entered.
h
m
From Location
To Location
For accurate daylight-saving conversion, choose locations such as New York and Los Angeles rather than fixed abbreviations such as EST or PST.
Shows the current date and time in each location using your device's clock. Updates about once a minute. Compare up to 6 locations at once.
You can compare up to 6 time zones at once.
Location
Current Date
Current Time
UTC Offset
Day vs. Home
Primary Time Zone
Additional Locations (up to 5)
You can add up to 5 additional locations (6 total).
Each location's local start time is checked against this range. A meeting outside this window is only labeled "Outside," never "bad."
A time zone calculator converts one moment into the local clock time used in another part of the world. That sounds like simple subtraction: New York is a certain number of hours from London, and Los Angeles is a certain number of hours from New York. The real calculation is more complicated because time zone offsets can change depending on location, date, daylight-saving rules, and government decisions.
A reliable converter should not simply store New York as UTC minus 5 and Los Angeles as UTC minus 8 as permanent facts. Those are standard-time offsets, but daylight-saving time can change them for part of the year. CalculateThisWay uses location-aware IANA time zone data through your browser's built-in time zone support, rather than a fixed table of offsets.
Visual: UTC as the Reference Point
Each local time zone is described as an offset ahead of or behind UTC. That offset can change across the year wherever daylight-saving time applies.
Example UTC offsets for four reference locations
Location
Typical Offset Range
New York
UTC-5 (standard) or UTC-4 (daylight)
UTC
Reference point, UTC+0
London
UTC+0 (standard) or UTC+1 (daylight)
Tokyo
UTC+9 year-round, no daylight-saving time
What Is the IANA Time Zone Database?
The IANA Time Zone Database, also called tz, tzdb, or zoneinfo, contains data representing the history and rules of civil time for regions around the world. Time zones commonly use names such as America/New_York, America/Los_Angeles, Europe/London, and Asia/Tokyo rather than a fixed number of hours. The database is updated when political authorities change time zone boundaries, UTC offsets, or daylight-saving rules.
This matters because civil time is not permanently fixed by geography alone. Governments can change the rules. CalculateThisWay uses the IANA rules available through modern browser time zone support, through the standards-based Intl.DateTimeFormat API, instead of maintaining a hand-built table of permanent offsets.
The IANA Time Zone Database is updated periodically. CalculateThisWay relies on standards-based IANA time zone rules available in your browser, which may occasionally lag a very recent legal change until that browser or operating system updates its data.
Why Does the Date Matter in a Time Zone Conversion?
Imagine converting 3:00 PM New York time to London time. The difference between those cities is not guaranteed to be the same on every calendar date. The United States and United Kingdom can begin or end daylight-saving time on different dates. For a short period between those transitions, the normal time difference can temporarily change. That means the city, the date, and the time are all important inputs. A good time zone converter should always know the exact date being converted, which is why the calculator above asks for one.
What Is UTC?
UTC stands for Coordinated Universal Time. Local time zones can be described using an offset from UTC. A local zone may use UTC-5 for one part of the year and UTC-4 during another part. CalculateThisWay shows the current offset used for the selected date in each result, so you can see why the conversion works.
GMT vs. UTC
GMT and UTC are often treated the same in casual time conversion, especially when discussing a zero-hour offset. Technically, they are not identical concepts. UTC is the international time standard used as the basis for modern civil-time coordination. GMT is a time zone and timekeeping term associated historically with Greenwich. For everyday conversion, the important point is to choose the actual location or UTC reference you intend, rather than assuming an abbreviation has one universal meaning.
EST vs. EDT
EST means Eastern Standard Time, corresponding to UTC-5. EDT means Eastern Daylight Time, corresponding to UTC-4. Many places in the U.S. Eastern time zone switch between these depending on the date. That is why the safer selector is New York, or America/New_York, rather than forcing yourself to decide between EST and EDT. The converter determines the appropriate offset for the entered date automatically.
Why Are Time Zone Abbreviations Confusing?
Some abbreviations are ambiguous. CST can refer to Central Standard Time in North America or China Standard Time in Asia. IST can refer to India Standard Time or Irish Standard Time, among others. Even familiar U.S. abbreviations can describe only the standard or daylight version of a zone. Use cities and IANA locations whenever accuracy matters, and treat abbreviations as a convenient search term rather than the primary selector.
How Do I Convert New York Time to Los Angeles?
Choose New York as the From location and Los Angeles as the To location, then enter the date and time. For many dates, Los Angeles is three hours behind New York, so 3:00 PM New York may become 12:00 PM Los Angeles. The calculator still applies the date-aware time zone rules instead of simply subtracting three hours, so the result stays correct even in the rare weeks when either zone's daylight-saving schedule shifts.
How Do I Convert New York Time to London?
Enter the exact date. This matters because the U.S. and U.K. daylight-saving schedules are not perfectly synchronized. On many dates, 3:00 PM New York may correspond to 8:00 PM London. At certain times of year, shown in the worked examples below, the difference can temporarily be four hours instead of five. The page shows the actual UTC offsets used for the chosen date so you can see exactly why.
Visual: Crossing Midnight
A time conversion can cross midnight in either direction. Always check both the date and the time in the result, never the clock time alone.
Example of a conversion crossing midnight
Zone
Local Clock Time
Calendar Day
Zone A
11:00 PM
Same day
Zone B
2:00 AM
Next day
Why Did the Converted Date Change?
A time conversion can cross midnight. Suppose a time in one country converts to 1:00 AM in another location. If the original location is still on the previous evening, the destination date can be one day later. The reverse can happen when converting westward, landing on the previous day. CalculateThisWay always shows both the date and the time together, with a clearly labeled Previous Day, Same Day, or Next Day badge, so the result is never a clock time by itself.
What Happens During Daylight Saving Time?
Some regions move clocks forward or backward during the year. Not every country uses daylight-saving time. Not every location within one country necessarily follows the same rule. Arizona is a familiar U.S. example where most of the state does not follow the same seasonal clock changes as many other U.S. locations. The correct rule belongs to the location, not merely a broad abbreviation.
Visual: Daylight-Saving Shift
This is a generic illustration. The actual date, hour, and length of a transition vary by zone, and not every zone observes daylight-saving time at all.
Generic daylight-saving transition behavior
Transition
Effect
Spring forward
Clocks jump ahead, for example 1:59 AM to 3:00 AM; the skipped clock time does not occur that day
Fall back
Clocks move back, for example from 2:00 AM to 1:00 AM; that hour's clock times occur twice
Why Can 2:30 AM Sometimes Not Exist?
During a spring-forward transition, clocks can jump forward. A clock may move from 1:59 AM directly to 3:00 AM. A local time such as 2:30 AM then does not occur on that date in that location. The calculator tells you the local time does not exist rather than silently changing it to something else, and it shows the two real moments on either side of the gap so you can choose a valid time.
Why Can 1:30 AM Happen Twice?
When clocks move backward, one hour can repeat. That means 1:30 AM may occur once before the clock change and once afterward. The two local clock readings look identical but correspond to different moments and different UTC offsets. For an exact conversion, the calculator shows both the earlier and the later occurrence rather than guessing which one you meant.
Does Every Country Use Daylight Saving Time?
No. Many do not. Some have stopped using it. Some have changed their rules. Some use rules that differ from neighboring countries. This is one reason a time zone calculator needs updated, location-based data rather than a permanent global chart.
What Time Is It in Another Time Zone Right Now?
The Compare Time Zones Now mode above displays the current local time in several selected locations, such as New York, Los Angeles, London, and Tokyo. It updates about once a minute. A constantly updating second-by-second clock adds little practical value and uses more browser resources than necessary.
How Do I Schedule a Meeting Across Time Zones?
Choose the meeting date, meeting time, and your primary location in the Meeting Planner mode above. Then add the other participants' locations. The planner shows the same moment translated into each location's local date and time. For example, 3:00 PM in New York can correspond to 8:00 PM in London and 5:00 AM the following day in Tokyo. The exact conversion depends on date-specific rules, which is why the planner always asks for a specific date.
Visual: Meeting Timeline
Every participant experiences the same underlying moment, just translated into their own local date and time. Figures shown are an illustrative example, not a fixed rule.
Example meeting timeline aligned to one shared moment
Location
Local Time
Calendar Day
New York
3:00 PM
Same day
London
8:00 PM
Same day
Tokyo
5:00 AM
Next day
What Is a Good International Meeting Time?
There is no universal best time. A convenient afternoon for one person can be the middle of the night for another. CalculateThisWay lets you define a preferred working-hours window, such as 8 AM to 6 PM, in the Meeting Planner, and shows which converted times fall inside that range. It does not declare that a person's outside-hours meeting is wrong, only that it falls outside the preferred window you set.
Time Zone Calculator vs. Time Calculator
Use the Time Zone Calculator when the clocks are in different geographic time zones. Use the Time Calculator when you need elapsed time, adding hours, subtracting minutes, or other clock arithmetic without changing time zones. Use the Date Calculator when the main question is what calendar date falls a number of days away. Use the Hours Calculator for work shifts and timesheets, and the Minute Calculator for short, minute-level time math.
Can Time Zone Rules Change?
Yes. Time zone and daylight-saving rules are created by governments and can change with relatively little notice. The IANA Time Zone Database is updated periodically to represent those changes. A browser or operating system can sometimes lag an extremely recent legal change until its time zone data is updated. For a critical international event immediately following a newly announced time zone law, confirm the current official local-time rule with an authoritative source before relying on any calculator.
The Bottom Line
Accurate time zone conversion requires more than memorizing offsets. It requires the location, the date, the local time, and current IANA time zone rules. CalculateThisWay shows both the converted time and date, the offsets used, and any daylight-saving ambiguity, so you understand exactly what happened and why.
Worked Time Zone Examples
The examples below are computed live in your browser using the same conversion engine as the calculator above, using your device's current IANA time zone data, not typed in as fixed text.
New York to Los Angeles, Winter Date
New York to London, Winter Date
New York to London, Temporary Offset Change
Tokyo to New York, Date Rollover
Phoenix to New York, Winter vs. Summer
Try It Yourself
It is 8:00 AM in Tokyo, Japan. What date and time is it in New York, United States?
Calculating using your device's current time zone rules...
Which Calculator Do I Need?
This Page
Time Zone Calculator
I want to convert a time between different geographic time zones, compare current times, or plan a meeting. (this page)
A time zone converter changes a date and time in one location into the matching date and time in another location, accounting for each location's UTC offset and any daylight-saving rule in effect on that date.
How do I convert time zones?
Choose the Convert a Date and Time mode above, enter a date and time, pick a From location and a To location, then press Convert. The calculator uses each location's current IANA time zone rules for that specific date.
What time is EST in PST?
Standard Eastern Time (EST) is typically three hours ahead of standard Pacific Time (PST). Because the Eastern and Pacific zones usually move into and out of daylight time on the same dates, the gap is commonly three hours year-round, but choosing New York and Los Angeles as locations lets the calculator confirm the offset for your exact date.
What time is PST in EST?
Standard Pacific Time (PST) is typically three hours behind standard Eastern Time (EST). Enter the exact date using the Los Angeles and New York locations above to see the precise offset used for that date.
What is CST to EST?
Standard Central Time is typically one hour behind standard Eastern Time. CST can also refer to China Standard Time, which is a completely different offset, so choosing a city such as Chicago rather than typing only an abbreviation avoids confusion.
What is UTC?
UTC stands for Coordinated Universal Time. It is the time standard used as the reference point for civil time around the world, and local time zones are commonly described as an offset ahead of or behind UTC.
What is GMT?
GMT stands for Greenwich Mean Time, a time standard historically associated with Greenwich, England. In everyday conversion it is often treated the same as a zero-hour offset, though UTC is the modern technical reference.
Is GMT the same as UTC?
For most everyday purposes, a zero-hour GMT offset and UTC are treated the same. They are not identical technical concepts, but the distinction rarely matters for ordinary time zone conversion.
What is EST?
EST stands for Eastern Standard Time, the standard-time offset of UTC minus 5 hours used in the U.S. Eastern time zone outside of daylight-saving months.
What is EDT?
EDT stands for Eastern Daylight Time, the UTC minus 4 hours offset used in the U.S. Eastern time zone while daylight-saving time is in effect.
What is PST?
PST stands for Pacific Standard Time, the standard-time offset of UTC minus 8 hours used on the U.S. Pacific coast outside of daylight-saving months.
What is PDT?
PDT stands for Pacific Daylight Time, the UTC minus 7 hours offset used on the U.S. Pacific coast while daylight-saving time is in effect.
Why should I select a city instead of EST?
A city or region such as New York automatically uses the correct standard or daylight offset for whatever date you enter. An abbreviation such as EST only describes standard time, so it can silently produce a wrong result during daylight-saving months.
Why are time zone abbreviations ambiguous?
Abbreviations such as CST and IST are used by more than one region with different offsets, and abbreviations such as EST describe only part of the year for locations that observe daylight-saving time. Choosing a location keeps the conversion accurate.
How many hours is New York from Los Angeles?
New York is commonly three hours ahead of Los Angeles, since both zones typically begin and end daylight-saving time on the same dates. Use the calculator with your exact date to confirm.
How many hours is New York from London?
New York is commonly five hours behind London. For a few weeks each spring and autumn, when the United States and United Kingdom change their clocks on different dates, the gap can temporarily become four hours instead.
What time is London in New York?
To see what a London time becomes in New York, use the Convert a Date and Time mode with London as the From location and New York as the To location, and enter the exact date you need.
What time is Tokyo in New York?
To see what a Tokyo time becomes in New York, use the Convert a Date and Time mode with Tokyo as the From location and New York as the To location. Because of the large offset, the result commonly falls on the previous calendar day in New York.
Can a time zone conversion change the date?
Yes. Converting a time into another time zone can move the result into the previous day, the same day, or the next day, depending on the time entered and the offset between the two locations.
Why is the result the previous day?
When converting into a time zone that is far enough behind the original location, an early-morning time can fall before midnight on the prior calendar date in the destination location.
Why is the result the next day?
When converting into a time zone that is far enough ahead of the original location, a late-evening time can fall after midnight, landing on the following calendar date in the destination location.
What is daylight saving time?
Daylight-saving time is a seasonal practice of setting clocks forward, typically by one hour, for part of the year, then setting them back later. Not every country or region follows this practice.
Do all countries use daylight saving time?
No. Many countries do not use daylight-saving time, some have stopped using it, and some regions within a country follow different rules than the rest of that country.
Why can 2:30 AM not exist?
During a spring-forward transition, clocks jump forward by an hour, for example from 1:59 AM directly to 3:00 AM. A clock time inside that skipped hour, such as 2:30 AM, never occurs on that date in that location.
Why can 1:30 AM happen twice?
During a fall-back transition, clocks move backward by an hour, so the clock repeats an hour such as 1:00 AM to 1:59 AM. A time inside that repeated hour corresponds to two different real moments with two different UTC offsets.
What is an IANA time zone?
An IANA time zone is a named entry, such as America/New_York, in the IANA Time Zone Database, which records the civil-time history and daylight-saving rules for that location rather than a single fixed offset.
Can time zone rules change?
Yes. Governments can change time zone boundaries, UTC offsets, and daylight-saving rules with relatively little notice, and the IANA Time Zone Database is updated periodically to reflect those changes.
Does Arizona use daylight saving time?
Most of Arizona does not observe daylight-saving time and stays on standard time year-round, which is why this calculator treats Phoenix separately from other U.S. Mountain-zone locations.
Can I compare several time zones?
Yes. The Compare Time Zones Now mode shows the current date, time, and UTC offset in up to six locations at once, updating automatically about once a minute.
How do I schedule an international meeting?
Use the Meeting Planner mode. Enter a proposed date, start time, and duration in your primary location, add the other participants' locations, and the planner shows each person's local start and end time along with whether it falls inside their preferred working hours.
Does the calculator update current times automatically?
The Compare Time Zones Now mode refreshes roughly once per minute using your device's clock. The Convert and Meeting Planner modes calculate once, when you press their button, based on the date and time you entered.
What is the difference between Time Zone Calculator and Time Calculator?
Use the Time Zone Calculator when the two clocks are in different geographic time zones. Use the Time Calculator for elapsed time, adding hours, or subtracting minutes within a single time zone.
Sources & Further Learning
Internet Assigned Numbers Authority (IANA): Time Zone Database. iana.org/time-zones
Bureau International des Poids et Mesures (BIPM): International timekeeping and UTC coordination. bipm.org/en/time-metrology
Methodology & Limitations
All conversions use your browser's built-in Intl.DateTimeFormat support for IANA time zone identifiers, so offsets and daylight-saving rules reflect the time zone data currently installed on your device rather than a fixed table.
No live API call is used or required for ordinary conversions, since the browser already contains the IANA rules needed to calculate offsets locally.
When a browser's time zone data has not yet been updated for an extremely recent legal change, results can briefly lag that change until the browser or operating system is updated.
A local time that is ambiguous, because clocks moved backward, is shown as two distinct results rather than guessed. A local time that does not exist, because clocks moved forward past it, is flagged and never silently reinterpreted.
The Compare Time Zones Now mode refreshes approximately once per minute rather than every second, to keep the page lightweight.
This calculator does not place entered dates, times, or selected zones into the page URL or into analytics events.
This calculator uses your browser's built-in IANA time zone data to estimate civil time, UTC offsets, and daylight-saving transitions. That data is updated periodically and can occasionally lag an extremely recent government change to time zone or daylight-saving law. For a critical event immediately following a newly announced time zone change, confirm the current official local time with an authoritative source such as the IANA Time Zone Database or a national timekeeping authority.