I work across time zones. In practice that means keeping three clocks in my head and being confidently wrong about one of them roughly once a week. A little tool to help me be wrong less often.
Tímabil is Icelandic for a period of time — tími (time) and bil (a gap). It is written in Reykjavík, which stopped changing its clocks in 1968 and never looked back (not really).
It opens on wherever you are. Add the places that actually matter to you; they are remembered, so it is a thing you do once and then stop thinking about.
Every place at the same moment, with a square of sky beside each one — so you can tell it is four in the morning for somebody before you have read a number. Both clocks are there too, because half the world says 16:00 and the other half says 4 PM.
Drag the numbers sideways and everything moves together.
Daylight saving? Reykjavík never changes its clocks; America does; Europe does it on a different Sunday; Australia does it in the opposite season. So the distance between two cities depends on which day you are asking about — and when you drag across one of those changes, the cities that moved say so.