Display analog and digital clocks for multiple cities simultaneously with daylight/nighttime indicators.
This dashboard draws one analog face and one digital readout per city you add, each driven by your device's system clock plus that city's current UTC offset, so every panel ticks forward together in real time rather than being a static snapshot. A small sun or moon marker beside each clock flags whether that city is presently in daytime or nighttime hours. What trips people up is that the offset applied is whatever is correct for today's date: a city added months ago can shift by an hour on its own when that region's daylight saving start or end date passes, even though nothing on screen was touched.
A concrete input and expected output from the current implementation.
Input
Add New York, London, and Tokyo, with the dashboard's reference moment at 14:00 UTC on 2026-08-16
Expected output
New York shows 10:00 (daytime marker), London shows 15:00 (daytime marker), Tokyo shows 23:00 (nighttime marker)
On that date New York runs EDT (UTC-4), London runs BST (UTC+1), and Tokyo's JST has no daylight saving (UTC+9), so 14:00 UTC becomes 10:00, 15:00, and 23:00 respectively.
Each city you add is resolved to its current UTC offset for today's date, including whether that region is presently observing daylight saving. Both the analog hands and the digital readout are derived from applying that offset to your device's own system clock, so the dashboard needs no network call to keep ticking but does depend on your device's clock and timezone data being correct.
Each panel's sun or moon icon reflects that city's local clock hour, switching around a fixed morning and evening threshold rather than computing that city's actual sunrise or sunset for the date. Near the solstices, or for cities at high latitude, this can flag it as 'day' or 'night' at an hour when the real sky looks different, since it is reading the clock, not the sun's position.
Yes, for the offset itself: it reads your device's current timezone data, which already encodes known daylight saving start and end dates for each region. It can't anticipate a country announcing a new DST rule that isn't yet in your operating system's timezone data.
No. It's a rough clock-hour cue meant for a quick glance, not an astronomical sunrise/sunset calculation for that city's coordinates and date. For exact daylight timing, use a dedicated sunrise/sunset calculator instead.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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