Sunset is later than 6:00 PM in Melbourne until 10 April, and again from 3 September.

Every day of the year, the sun's altitude is computed for this place from its geometry alone — the same arithmetic as every other instrument here — and the minute it crosses each definition is found to the second: sunset with the sun's upper edge on the horizon (its centre at −0.833°, the standard allowance for refraction), civil dusk with the centre 6° below (light enough to walk by without lamps), and the golden hour beginning with the centre 6° above. Each is read in the clock time of the place's zone, using the zone tables the browser itself carries, so the clock changes appear as they are lived: an hour's step in the curve on the day the clocks move.

The line is the hour you finish. A crossing is the first day the evening event falls in a later minute than that hour, and the last day it does — the minute being the one the sunset page shows, the first whole minute with the sun past the mark. When a clock change is what moves a crossing, the drawing marks it, and marks the day the sun alone would have reached the same hour under the zone's standard time. The dates are exact to the day for a flat horizon; hills, buildings and the atmosphere of a particular evening can move any one event by minutes, never a crossing by more than a day or two.

New York, London and Melbourne are baked nightly so a search engine can read the answer; the same engine runs in your browser for any place, any year and any hour, from the line you drag. The full year is published beside each city page as JSON, CC BY 4.0.