ChronoUnitDAYS

ChronoUnitDAYS refers to the days unit within the ChronoUnit enumeration, a standard part of the Java date-time API introduced in Java 8 (JSR-310). The canonical name is ChronoUnit.DAYS, and it represents the unit of calendar days used for measuring temporal amounts and performing date-time arithmetic.

In practice, ChronoUnit.DAYS is used to count or advance by whole days. Common operations include calculating the number of days between two temporals (for example, between two dates or date-times) and adding or subtracting a number of days to a temporal object. Examples of typical usage are calculating the difference in days between two LocalDate values or moving a date-time forward by a specified number of days using plus or minus with ChronoUnit.DAYS.

Notes and caveats are important when using this unit. For calendar days on date-based types like LocalDate, the difference corresponds to calendar days. When working with time-based types such as LocalDateTime or ZonedDateTime, the interpretation can be influenced by time zones and daylight saving time transitions, so two moments separated by a DST change may affect how many days apart they appear if time components are included. If the goal is to count calendar days regardless of time or zone, converting to LocalDate first is a common approach.

ChronoUnit.DAYS is one of several fixed-duration units in ChronoUnit, alongside HOURS, MINUTES, SECONDS, and others. It is designed for straightforward day-level calculations within the ISO calendar system and related temporal types. See also ChronoUnit, TemporalUnit, and the broader java.time API.