Does this handle daylight saving automatically?

Yes — each city's real local time, including daylight saving, is computed automatically.

No — timezone math runs locally in your browser.

Yes — free, no download, in your browser.

Yes — it recomputes every second against your device's real clock.

Why do overlaps change twice a year?

Daylight saving transitions happen on different dates in different countries, and some regions do not observe it at all. For a few weeks the gap between two cities can differ by an hour from its usual value.

Which places use unusual offsets?

India and Sri Lanka use UTC+05:30, Nepal uses UTC+05:45 and Eucla in Western Australia uses UTC+08:45. These shift the overlap by a fraction of an hour.

World Business Hours Overlap Screensaver

The World Business Hours Overlap screensaver shows which major world cities currently have overlapping working hours, computed from each city's real current local time. It is free, runs in your browser, and ESC exits.

How the World Business Hours Overlap screensaver works

The saver computes each listed city's real current local time using standard timezone data, including daylight saving automatically.

Cities currently within a real 9am–5pm working window are highlighted as "in business hours".

The board updates live every second as real time passes.

No network fetch is required — timezone rules are resolved locally by the browser.

Time zones and the shrinking shared workday

Time zones are nominally about fifteen degrees of longitude wide, but political decisions make the real map irregular. India and Sri Lanka use UTC+05:30, Nepal uses UTC+05:45, and Western Australia’s Eucla uses UTC+08:45. Many countries also shift their clocks for daylight saving on different dates. The saver relies on standard timezone data, the IANA database, to know these rules.

Overlap matters because a nine-to-five day covers only eight of the twenty-four hours. California in winter is UTC−08:00 and Singapore is UTC+08:00, a sixteen-hour gap, so a nine-to-five day in one is the middle of the night in the other and the two share no standard working hours. Teams in that position rely on early or late calls or asynchronous work.

Treat the highlights as arithmetic, not working life. Many people do not keep nine-to-five hours, and weekends differ: Saudi Arabia, Kuwait and Qatar, for example, have a Friday–Saturday weekend, while many countries use Saturday–Sunday. Public holidays are not considered. The display tells you whether the clocks align, not whether anyone is at a desk.

A worked example

When it is mid-morning in New York, London's real local time might already be mid-afternoon — both fall inside working hours, so both light up as overlapping.

Settings & tips

Accent recolours the highlighted cities.
Daylight saving is handled automatically for each real city.
Useful at a glance for scheduling across time zones.

Frequently asked questions

Does this handle daylight saving automatically?: Yes — each city's real local time, including daylight saving, is computed automatically.
Is a key needed?: No — timezone math runs locally in your browser.
Is it free?: Yes — free, no download, in your browser.
Is this live?: Yes — it recomputes every second against your device's real clock.
Why do overlaps change twice a year?: Daylight saving transitions happen on different dates in different countries, and some regions do not observe it at all. For a few weeks the gap between two cities can differ by an hour from its usual value.
Which places use unusual offsets?: India and Sri Lanka use UTC+05:30, Nepal uses UTC+05:45 and Eucla in Western Australia uses UTC+08:45. These shift the overlap by a fraction of an hour.

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