Build a time zone converter and meeting planner that knows about summer time
The hard part of working across time zones isn't adding hours; it's the weeks in spring and autumn when clocks change on different dates, and finding the one hour everyone is awake. A time zone converter built with Anticode uses the browser's own time-zone data, so it needs no network and handles summer time, and can show your team's working hours side by side.
Why offsets aren't fixed
"London is five hours ahead of New York" is true for most of the year, but not all of it. The UK and the US change their clocks on different dates, so for a few weeks each spring and autumn the gap is four hours. Some places don't use summer time at all, some are offset by half or three-quarters of an hour, and the southern hemisphere changes in the opposite season.
So a converter shouldn't store offsets. It should store named zones, such as Europe/London, America/New_York or Asia/Kolkata, and ask the browser what the local time is in each zone for the date in question. Modern browsers carry this time-zone database built in, which is why the app needs no network. It's kept up to date as browsers update.
The screens
- Converter
- Pick a date and time in one city; see it in every other city on your list, with the day shown when it changes ("Tue" against "Wed").
- World clock
- Your cities with the current time, live, and a day or night marker. Useful pinned on a second screen.
- Meeting planner
- A row of hours per city, coloured by working hours, sleeping hours and the grey edges in between. Drag a highlight across to find the overlap, or let the app suggest the hours where everyone is inside working time.
- Shareable line
- A sentence you can paste into an invitation: "Thu 14 Nov, 15:00 London / 10:00 New York / 20:30 Delhi".
Working hours, per person
A time zone meeting planner gets far more useful when it's about people, not just cities. Add each colleague with their zone and their own hours: someone in Sydney might start at 7, someone in Berlin finishes early on Fridays. Mark days off for public holidays you know about. The suggestion then becomes "the best hour for these five people on Thursday", which is the real question.
When there is no good hour, say so, and show the least bad options with who's affected. Rotating the inconvenient slot between regions is fairer than always asking the same people to dial in at 10 p.m.
A description that works
"A meeting planner across time zones for our team. People: Ana in Lisbon 9-17, Tom in London 8-16, Priya in Bangalore 10-18, Jess in Chicago 9-17, Kai in Sydney 8-16. Use named time zones and the browser's time-zone data. A day view with one row per person, hours coloured green for working, amber for an hour either side, grey for night. Pick a date and suggest the best slots. A copy-ready line with the time in each city. A world clock tab. Light, quiet, dense like a calendar."
Anticode's model writes it as one app. The people and their hours are saved in that browser, so the list is there when you return. Test it on a date in the week the clocks change, such as the end of March, and check the gap between your cities against a reliable source.
What it doesn't do
- No calendar access. It can't read anyone's calendar or see when they're busy, and it can't send invitations. Copy the line into your calendar tool.
- No shared team list. Each person who opens the published app has their own list. Ask for an export and import so you can hand a teammate the same setup.
- No public holidays database. Add the ones that matter yourself; there's no network to fetch them.
- No location detection. It uses the device's own time zone setting, not its position.
If your planning is really about bookings with clients in other zones, Anticode's booking calendar for published sites is the tool to look at, with its own limits. For converting other measures, see the unit converter app; for remote events, the countdown timer app covers launch times in named zones.
Questions people ask
Does the time zone converter need the internet?
No. It uses the time-zone data built into your browser, so it works once loaded. Installed sites have an offline fallback; test opening it offline before relying on it.
Does it handle half-hour offsets like India?
Yes, if it uses named zones and the browser's data, which you should ask for explicitly.
Can it show times in 12-hour format?
Ask for a 12-hour or 24-hour setting, saved in your browser.