daysuch

Daysuch is a neologism used in discussions of timekeeping to denote a day defined by a specific criterion rather than the conventional civil day that runs from midnight to midnight. In practice, a daysuch may be any day that meets a preselected condition—such as an astronomical event, a weather pattern, or a sociocultural marker—after which a calendar could reset, realign, or label time differently. The concept is primarily described as a thought experiment or a proposed feature for alternative calendars rather than an established system.

Origin and usage: The term has appeared in online forums, speculative essays, and fictional contexts since the early 21st century. It is not standardized or officially adopted by timekeeping authorities. Daysuch is typically discussed as a flexible idea that helps explore how calendars might respond to environmental signals, cultural cycles, or algorithmic scheduling, rather than as a fixed method of measuring time.

Mechanics and examples: A daysuch is defined by one or more criteria applied to determine the moment that begins or ends the day. Examples include a day defined by a dominant astronomical alignment, a day marking peak solar radiation, or a day designated by a local festival. In such frameworks, the length of a daysuch remains a day-sized interval, but its labeling and initiation may shift to reflect the chosen criterion.

In fiction and theory: Daysuch is often used as a narrative device to drive plot or to test the stability of calendar systems under unusual rules. It is also discussed as a conceptual tool for environmental planning, cultural timing, or studies of time perception.

See also: timekeeping, calendar reform, chronometry.