Zonnetime

Zonnetime is a proposed timekeeping concept that ties civil time to the Sun’s position in the sky rather than to fixed time zones. It represents a continuous global time coordinate, called Z-Time, from which local times are derived.

In zonnetime, a location’s local zonnetime offset is computed from its longitude: the offset equals longitude in degrees times 4 minutes, with positive values east of the prime meridian. Z-Time advances uniformly in real time; local zonnetime equals Z-Time plus the longitude offset, adjusted to a 24-hour day. The reference meridian can be chosen so that midnight in the reference zone aligns with a solar midnight.

Operation and transitions: As the Sun's position changes, local time tracks solar noon and sunrise/sunset; the system supports gradual transitions at borders using smoothing functions to avoid abrupt clock changes, creating continuous local times across longitudes.

History and usage: Zonnetime has appeared in theoretical discussions of global timekeeping and in science fiction as a way to synchronize activities across continents with daylight patterns. Some proponents argue it reduces jet lag and improves scheduling; critics point to complexity, compatibility with existing systems, and the need for astronomical data.

See also: time zone, solar time, universal time, international date line.