Manipulate

Operations that yield a new value of the receiver's type. They return raw Temporal, so the native chain carries on:

const today = Temporal.PlainDate.from("2026-10-06");

Chronos(today).startOf("month").add({ days: 14 }); // 2026-10-15

startOf

startOf(unit: UnitOf<T>): T

The first value of the unit that contains the receiver. Weeks start on Monday.

const today = Temporal.PlainDate.from("2026-10-06"); // a Tuesday

Chronos(today).startOf("month"); // 2026-10-01
Chronos(today).startOf("week"); // 2026-10-05

const now = Temporal.PlainDateTime.from("2026-10-06T14:35:12");
Chronos(now).startOf("hour"); // 2026-10-06T14:00:00

On a ZonedDateTime, a day starts when its zone says, which is not always midnight. On an Instant, units are floored in UTC.

endOf

endOf(unit: UnitOf<T>): T

The last value of the unit that contains the receiver: the last day on a PlainDate, otherwise one nanosecond before the next unit starts.

Chronos(today).endOf("month"); // 2026-10-31
Chronos(now).endOf("day"); // 2026-10-06T23:59:59.999999999

clamp

clamp(a: T, b: T): T

The receiver limited to the range between a and b, in either order.

const first = Temporal.PlainDate.from("2026-10-10");
const last = Temporal.PlainDate.from("2026-10-31");

Chronos(today).clamp(first, last); // 2026-10-10
Chronos(today).clamp(last, first); // 2026-10-10: either order

Errors

clamp throws a TypeError if a bound is not of the receiver's type. startOf and endOf throw a RangeError if unit is not a unit, or one the receiver's type lacks, such as "hour" on a PlainDate.