Synchrona

Synchrona shows the current time in every city you care about, on one screen you can read from across the room. It follows your light or dark appearance. 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 is the blue row, and it follows you when you travel. Times use your region's 12- or 24-hour clock unless you pick one in Settings. Add a city by searching for it. The list starts with twenty common cities, and search finds any time zone by name. Hold a card and drag to reorder, or swipe left to remove one. 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.