Time Zone Calculator — Free Online Time Zone Converter

How to Use the Time Zone Calculator

1. Enter the time to convert: Input the hour (0-23) and minute (0-59) you want to convert. Use 24-hour format where 1 PM is 13, 6 PM is 18, and midnight is 0. The default is 12:00 (noon).
2. Select the source time zone: Choose the time zone of your input time from the "From Time Zone" dropdown. Each option displays the UTC offset and a representative city (for example, "UTC-5 (New York)" or "UTC+9 (Tokyo)"). The default source is UTC+0 (London).
3. Select the target time zone: Choose the destination time zone from the "To Time Zone" dropdown. The default target is UTC-5 (New York), showing the common London-to-New-York conversion.
4. Read the converted result: The results panel immediately shows the converted time, the source time for reference, the offset difference between the two zones, and a date change indicator if the conversion crosses midnight. The conversion summary at the bottom clearly states both times with their respective time zones.

All results update instantly when you change any input. Try converting the same time to multiple zones by changing the "To Time Zone" dropdown to compare business hours across international offices.

Time Zone Conversion Formula

Variables Explained

• Source Time: The time you are converting from, expressed in the source time zone. For example, 14:00 in Tokyo (UTC+9).
• Source Offset: The UTC offset of the source time zone, in hours. Tokyo is +9, New York is -5, London (GMT) is 0.
• UTC Time: The intermediate result after removing the source offset. This is the universal reference point that all time zones share.
• Target Offset: The UTC offset of the destination time zone, in hours. The target time is UTC plus this offset.
• Offset Difference: Target Offset minus Source Offset. This is the number of hours to add (or subtract, if negative) to the source time. For Tokyo (+9) to New York (-5), the difference is -14 hours.

Step-by-Step Example

Convert 15:30 in Dubai (UTC+4) to Los Angeles (UTC-8):

1. Source time: 15:30, Source offset: +4
2. Convert to UTC: 15:30 - 4:00 = 11:30 UTC
3. Target offset: -8
4. Convert to target: 11:30 + (-8:00) = 03:30
5. Or directly: Offset difference = -8 - (+4) = -12 hours
6. 15:30 + (-12:00) = 03:30
7. Since 03:30 is the same calendar day: no date change
8. Result: 03:30 UTC-8 (Los Angeles)

When it is 3:30 PM in Dubai, it is 3:30 AM in Los Angeles. This 12-hour difference means there is minimal overlap in standard business hours between these two cities.

Practical Examples

Example 1: Raj's International Team Meeting

Raj manages a software team with members in Bangalore (UTC+5:30), Berlin (UTC+1), and San Francisco (UTC-8). He needs to find a meeting time that works for everyone. He starts with 18:00 Bangalore time and converts:

• 18:00 UTC+5:30 (Bangalore) = 13:30 UTC+1 (Berlin) = 04:30 UTC-8 (San Francisco)
• Berlin: 1:30 PM, acceptable
• San Francisco: 4:30 AM, too early

Raj tries 21:30 Bangalore time instead:

• 21:30 UTC+5:30 = 17:00 UTC+1 = 08:00 UTC-8
• Berlin: 5:00 PM (end of day but feasible), San Francisco: 8:00 AM (start of day)

The 21:30 Bangalore / 17:00 Berlin / 08:00 San Francisco slot works for all three locations, though it requires a late evening for Raj. For world clock tracking, our current time calculator shows live time in any zone.

Example 2: Emily's International Flight Planning

Emily is flying from London (UTC+0) to Tokyo (UTC+9). Her flight departs at 10:00 London time and takes 11 hours 30 minutes. She wants to know her arrival time in Tokyo local time:

• Departure: 10:00 UTC+0 (London)
• Flight time: 11 hours 30 minutes
• Arrival in London time: 10:00 + 11:30 = 21:30 UTC+0
• Convert to Tokyo: 21:30 + 9:00 = 06:30 (+1 day)
• Arrival: 06:30 Tokyo time the next day

Emily arrives at 6:30 AM the next day in Tokyo. Despite an 11.5-hour flight, she arrives 20.5 hours later in local time due to the 9-hour time zone difference. This is useful for planning hotel check-in and ground transportation.

Example 3: Carlos's Cryptocurrency Trading Window

Carlos lives in Buenos Aires (UTC-3) and wants to trade during peak hours on the New York Stock Exchange (NYSE), which operates 9:30-16:00 UTC-5. He converts the NYSE hours to his local time:

• NYSE open: 09:30 UTC-5 = 11:30 UTC-3 (Buenos Aires)
• NYSE close: 16:00 UTC-5 = 18:00 UTC-3 (Buenos Aires)
• Offset difference: -3 - (-5) = +2 hours

Carlos needs to be active from 11:30 AM to 6:00 PM Buenos Aires time to coincide with NYSE trading hours. The 2-hour offset means both cities share significant business hour overlap, making it convenient for real-time market participation.

Major Time Zones Reference Table

Tips and Complete Guide

Scheduling Across Time Zones

When scheduling international meetings, aim for the overlap window between participants' business hours (typically 9:00-17:00 local time). The wider the time zone gap, the smaller the overlap. Between New York (UTC-5) and London (UTC+0), there is a 5-hour offset with good overlap from 14:00-17:00 London / 09:00-12:00 New York. Between New York and Tokyo (UTC+9), the 14-hour offset means there is almost no business-hour overlap, requiring one party to attend outside normal hours.

Daylight Saving Time Awareness

Daylight saving time (DST) shifts clocks forward by one hour in spring and back in fall. Not all countries observe DST, and those that do may change on different dates. The US shifts on the second Sunday of March and the first Sunday of November; the EU shifts on the last Sundays of March and October. During the transition weeks, the offset between two locations may change by one or even two hours depending on whether both or only one observes DST. Always verify the current DST status of both locations when making time-sensitive conversions.

Time Zones and International Travel

When traveling across time zones, your body's internal clock (circadian rhythm) takes about one day per time zone crossed to fully adjust. This means a trip from New York to London (5-hour shift) may require up to five days for complete adaptation. To minimize jet lag, gradually shift your sleep schedule before departure, stay hydrated during the flight, and expose yourself to sunlight at your destination to help reset your circadian rhythm. Our date calculator can help plan travel itineraries with exact date differences.

Time Zones in Computing

In software development, handling time zones correctly is notoriously challenging. Best practices include storing all timestamps in UTC in databases, converting to local time only at the display layer, using established libraries (such as Intl.DateTimeFormat in JavaScript or pytz in Python) rather than manual offset arithmetic, and always storing the time zone alongside any local time. The IANA Time Zone Database (tzdata) is the authoritative source for time zone rules and is updated multiple times per year to reflect political changes.

Common Mistakes to Avoid

• Forgetting DST changes: The offset between two cities can change by one or two hours during DST transitions. A meeting that works at 09:00 in March may need adjustment in April when one country has shifted and the other has not.
• Confusing time zone abbreviations: "CST" can refer to Central Standard Time (UTC-6), China Standard Time (UTC+8), or Cuba Standard Time (UTC-5). Always use UTC offsets for clarity, especially in international communication.
• Ignoring date changes: Converting late-night times to distant time zones often results in a different calendar date. Always check the date change indicator to avoid scheduling meetings or flights on the wrong day.
• Assuming all time zones are whole hours: India (UTC+5:30), Iran (UTC+3:30), Nepal (UTC+5:45), and several Australian zones use non-integer offsets. Forgetting these fractional offsets leads to 30-or-45-minute scheduling errors.
• Not considering the date line: Regions near the International Date Line (like Samoa, Tonga, and Kiribati) have offsets of UTC+13 or UTC+14, meaning they can be a full day ahead of UTC-12 locations despite geographic proximity.

Frequently Asked Questions