Time Zone Calculator

Step 1: Enter the time you want to convert using the Hour and Minute fields (24-hour format). For example, 14 and 30 for 2:30 PM.

Step 2: Enter the UTC offset of your source time zone in the "From" field. US Eastern is -5, US Pacific is -8, UK is 0, India is 5.5, Japan is 9.

Step 3: Enter the UTC offset of the target time zone in the "To" field.

Step 4: Click Calculate. The result shows the converted time and whether it falls on the next day or previous day relative to the source.

Time zones divide the Earth into 24 regions, each roughly 15 degrees of longitude wide, where all clocks show the same time. The system is based on Coordinated Universal Time (UTC), which replaced Greenwich Mean Time (GMT) as the international standard in 1960.

UTC offsets express how many hours ahead or behind UTC a time zone is. UTC-5 (US Eastern Standard Time) is 5 hours behind UTC. UTC+5:30 (India Standard Time) is 5 hours and 30 minutes ahead. The offsets range from UTC-12 to UTC+14.

Key US time zones:
- Eastern (ET): UTC-5 (UTC-4 during daylight saving)
- Central (CT): UTC-6 (UTC-5 during DST)
- Mountain (MT): UTC-7 (UTC-6 during DST)
- Pacific (PT): UTC-8 (UTC-7 during DST)

Daylight Saving Time (DST) shifts clocks forward by 1 hour in spring and back in fall. Not all regions observe DST — Arizona, Hawaii, and most countries near the equator do not. When using this calculator during DST, use the adjusted offset (e.g., UTC-4 for US Eastern during summer, not UTC-5).

Half-hour and quarter-hour offsets exist. India uses UTC+5:30, Nepal uses UTC+5:45, and parts of Australia use UTC+9:30. Enter these as decimal values (5.5, 5.75, 9.5).

Converted Hour = Original Hour + (Target Offset − Source Offset)

If the result is ≥ 24: subtract 24 (next day)
If the result is < 0: add 24 (previous day)

Example: Convert 14:30 from UTC-5 (New York) to UTC+5:30 (Mumbai).
- Difference: 5.5 − (−5) = 10.5 hours
- New hour: 14 + 10.5 = 24.5 → 0:30 (next day)
- Result: 00:30 the next day in Mumbai

Common conversions from US Eastern (UTC-5):
- To UK (UTC+0): add 5 hours
- To Central Europe (UTC+1): add 6 hours
- To India (UTC+5:30): add 10.5 hours
- To Japan (UTC+9): add 14 hours
- To US Pacific (UTC-8): subtract 3 hours

Example 1: New York to London
It is 14:30 (2:30 PM) in New York (UTC-5). What time is it in London (UTC+0)? Enter hour 14, minute 30, from -5, to 0. Result: 19:30 (7:30 PM in London). London is 5 hours ahead.

Example 2: San Francisco to Tokyo
It is 09:00 in San Francisco (UTC-8). What time is it in Tokyo (UTC+9)? Enter hour 9, minute 0, from -8, to 9. Result: 02:00 (next day). Tokyo is 17 hours ahead — when it is morning in California, it is already the next morning in Japan.

Example 3: Mumbai to New York
A call is scheduled at 21:00 (9 PM) in Mumbai (UTC+5.5). What time is that in New York (UTC-5)? Enter hour 21, minute 0, from 5.5, to -5. Result: 10:30 (same day). The 10.5-hour difference means the call is at a reasonable morning time in New York.

Use DST-adjusted offsets. During daylight saving time (March-November in the US), add 1 to the standard offset. US Eastern goes from UTC-5 to UTC-4. Check whether DST is active in both the source and destination.

Half-hour offsets are entered as decimals. India (UTC+5:30) is entered as 5.5. Nepal (UTC+5:45) is 5.75. Australia's half-hour zones are 9.5, 10.5, etc.

"Next day" and "previous day" matter. A meeting at 22:00 UTC-5 is 03:00 the next day in UTC+0. Make sure all parties confirm the correct date, not just the time.

Not all regions observe DST. Arizona, Hawaii, most of Asia, Africa, and South America do not change clocks. Verify both time zones before scheduling international calls.

Consider the International Date Line. When crossing from UTC+12 to UTC-12, the date changes. Flying from Tokyo to Honolulu, you may arrive "before" you departed because of the date line.