Cities are sorted west to east by their current UTC offset. "Hide" keeps a city in the list without showing its tile. The home city (highlighted) is the one other tiles show their hours ahead or behind; use "Make home" to change it. Changes are saved in this browser only. To make them permanent for everyone, copy the JSON and replace the contents of cities.json.
Weather from Open-Meteo (free, no account), refreshed every 10 minutes. City search uses Open-Meteo's geocoder. Times come from your computer's clock, checked against the web server's clock (to about a second) and corrected if it's off.