Synchrona

Synchrona shows the current time in every city you care about, on one dark screen you can read from across the room. The slider along the bottom is the main idea. Drag it and every city shifts together, so you can see what 4 PM your time looks like in Tokyo, London, and Sydney before you send the invite. A colored strip under the slider runs from midnight blue through sunrise orange to noon amber and back to night, so you always know which part of the day you are pointing at. Let go and the slider settles on the nearest five minutes. Each city card shows the time in large, light digits, the zone abbreviation, and a sun or moon for day and night. When a city is already on tomorrow or still on yesterday, a +1 DAY or -1 DAY marker appears next to the time. Your own time zone stays pinned in blue at the top of the list. Add cities from a built-in list of 20 world cities. Remove one with a long press. Your list is saved on the device and nowhere else. Synchrona has no accounts and makes no network requests. Synchrona runs on iPhone, iPad, and Mac.