time zone conversion and UTC offsets
Converting time across zones looks like plain subtraction until daylight saving enters the picture. A place's UTC offset is not a fixed constant all year, it changes on specific dates across much of the world, and ignoring that is the most common reason a meeting ends up scheduled at the wrong hour.
São Paulo is only 1 hour ahead of New York in August because US daylight saving narrows the usual gap; Tokyo is already in the small hours of the next day because of the 13-zone distance.
It is the same "New York" from the previous example, but in January daylight saving is no longer active, and the offset shifts back a full hour: converting using August's offset would be off by a whole hour.
All of India runs on a single half-hour offset, an administrative decision dating back to post-independence unification; a converter that only adds whole hours cannot represent that offset correctly.
Yes. Because we use the browser's IANA time zone database, each city's offset is computed for the exact date you choose, automatically applying daylight saving when it is in effect for that zone at that time of year. That is why the difference between two cities can change depending on the month of the conversion.
Because the United States still observes daylight saving: under the Energy Policy Act of 2005, clocks move forward 1 hour on the second Sunday of March (EDT begins, UTC-4) and move back on the first Sunday of November (EST resumes, UTC-5). It is the same city and the same geographic zone, only the legal offset changes.
Not since 2019, when the federal government decided not to renew the provisional measure that kept it in place. Before that, parts of Brazil alternated between UTC-2 and UTC-3 in the summer; today São Paulo and most of the country stay fixed at UTC-3 all year, so the gap to zones that still observe daylight saving now varies with the season.
Because the whole country, east to west, adopted a single administrative zone instead of splitting its territory into multiple geographic zones, and that zone was fixed exactly halfway between UTC+5 and UTC+6. Nepal went further and adopted UTC+5:45, a 15-minute offset, also by national decision rather than astronomical convention.
Yes, on the exact day daylight saving begins. The local clock jumps straight from one minute to another that is already an hour later, so a time like "2:30 in the morning" simply does not correspond to any real instant in that zone on that day; converting it means treating the moment as either just before or just after the jump.
Conversions use your browser's time zone database and run locally. Nothing is sent to any server.