A timezone converter answers a different question from an epoch converter. The epoch converter tells you which instant a number represents. This tool takes a date and time in one timezone and shows the same instant in other locations.

Use IANA names, not abbreviations

Choose names such as America/New_York, Europe/London, and Asia/Tokyo. They carry the historical offset and daylight-saving rules for a location. Abbreviations such as CST and IST are overloaded, and a fixed offset such as UTC-5 does not describe a region that changes clocks.

Keep two concepts separate

  • An instant is a point on the UTC timeline, often stored as a Unix timestamp.
  • A local date and time is a wall-clock reading that needs a timezone before it identifies an instant.
  • A UTC offset is a numeric difference from UTC at one moment; it can change when daylight saving time starts or ends.

For storage, use a timestamp or UTC value. For recurring business schedules, also keep the IANA timezone so “9:00 AM every Monday” continues to mean the local wall-clock time users expect.

Epoch to DateDate to EpochUTC TimeEastern Time

Frequent questions:

Q: What is the difference between UTC and GMT?
A: UTC (Coordinated Universal Time) and GMT (Greenwich Mean Time) are nearly identical for everyday use: both sit at the zero meridian with no UTC offset. The technical difference is that GMT is a timezone based on mean solar time at the Royal Observatory in Greenwich, while UTC is an atomic time standard. Most programming contexts use UTC.
Q: How does daylight saving time affect Unix timestamps?
A: Unix timestamps are not affected by daylight saving time because they are always measured in UTC seconds. DST only affects the display of a timestamp when it is converted to a local timezone. This converter applies the correct DST offset for the selected timezone and date automatically.
Q: What is an IANA timezone identifier?
A: An IANA timezone identifier (also called an Olson timezone name) is a string like 'America/New_York' or 'Asia/Tokyo' that uniquely identifies a timezone region and its full history of UTC offsets and DST rules. They are maintained in the IANA Time Zone Database and supported by all major operating systems and programming languages.
Q: Should I store UTC or local time in my database?
A: Always store UTC (or Unix timestamps) in your database. Store the user's timezone preference separately and convert to local time only at display time. This avoids ambiguity during DST transitions and makes cross-timezone comparisons reliable.