By TimeThere · Updated
UTC gives people in different time zones a shared reference. An offset describes how far a local clock is ahead of or behind UTC at a particular instant. It does not identify a place or describe all its future clock changes.
Read the sign before doing the arithmetic
UTC+9 means local time is nine hours ahead of UTC. At 12:00 UTC, Seoul shows 21:00. UTC−5 means five hours behind: at that same instant, a city using that offset shows 07:00. To convert a local time to UTC, subtract its offset; to convert UTC to a destination, add the destination’s offset.
Keep the minutes
Mumbai uses UTC+5:30 and Kathmandu uses UTC+5:45 in the 2026 reference. At 12:00 UTC they show 17:30 and 17:45. The difference is fifteen minutes. Rounding either offset to a whole hour would give the wrong appointment time.
A conversion that crosses midnight
On January 15, 2026, 09:00 in Kathmandu is 03:15 UTC. New York is using UTC−5 on that date, so it is 22:15 on January 14 in New York. The hour and the calendar date must both appear in an invitation.
Adding a duration and changing a time zone are different operations. A 60-minute meeting beginning at 23:30 ends on the next local date. Switching cities preserves the instant, even if the displayed date changes.
A named time zone is safer for future dates
America/New_York identifies a set of time zone rules. UTC−5 is only an offset. New York uses UTC−4 during part of 2026, so choosing a permanent UTC−5 clock for a July meeting would be one hour wrong. Enter the city and the actual date in the converter instead.
AM, PM and midnight
In the 12-hour format, 12 AM is midnight and 12 PM is noon. In the 24-hour format, use 00:00 for the start of a day and 12:00 for noon. TimeThere offers both formats; changing the format does not change the moment. For a midnight deadline, write the full date and time zone rather than “midnight on Friday,” which can be interpreted in different ways.
For the underlying rules and accuracy limits, see our calculation methodology. For clock changes, see daylight saving time.