Query

Comparisons of the receiver against another value of its type. Each returns a boolean.

const today = Temporal.PlainDate.from("2026-10-06");
const deadline = Temporal.PlainDate.from("2026-10-20");

Chronos(today).isBefore(deadline); // true
Chronos(today).isSame(deadline, "month"); // true
Chronos(today).isSame(deadline, "week"); // false

Comparing by unit

Every method takes an optional unit. With a unit, the receiver stands for the whole unit that contains it, as in Day.js: isSame(other, "month") is true for any other in the receiver's month, and isBefore(other, "day") only once other is on a later day. Weeks start on Monday.

Units follow the receiver: see Units and types.

isBefore

isBefore(other: T, unit?: UnitOf<T>): boolean

Whether the receiver is strictly before other.

isAfter

isAfter(other: T, unit?: UnitOf<T>): boolean

Whether the receiver is strictly after other.

isSame

isSame(other: T, unit?: UnitOf<T>): boolean

Whether the receiver is the same point in time as other. On a ZonedDateTime, zone and calendar are ignored, as in Day.js; with a unit, the receiver's zone decides where the unit starts and ends.

isSameOrBefore

isSameOrBefore(other: T, unit?: UnitOf<T>): boolean

Whether the receiver is the same as or before other.

isSameOrAfter

isSameOrAfter(other: T, unit?: UnitOf<T>): boolean

Whether the receiver is the same as or after other.

isBetween

isBetween(from: T, to: T, options?: BetweenOptions<T>): boolean

Whether the receiver lies between from and to. Either bound order works, as in Day.js. Bounds are excluded unless the options say otherwise:

const start = Temporal.PlainDate.from("2026-10-06");
const end = Temporal.PlainDate.from("2026-10-20");

Chronos(start).isBetween(start, end); // false: bounds are excluded
Chronos(start).isBetween(start, end, { inclusive: true }); // true
Chronos(start).isBetween(start, end, { includeStart: true }); // true
Chronos(start).isBetween(end, start, { inclusive: true }); // true: either order

Option	Type	Meaning
inclusive	boolean	Whether both bounds count
includeStart	boolean	Whether the earlier bound counts; overrides inclusive
includeEnd	boolean	Whether the later bound counts; overrides inclusive
unit	UnitOf<T>	Compare by unit; an excluded bound excludes its whole unit

isToday, isTomorrow, isYesterday

isToday(): boolean
isTomorrow(): boolean
isYesterday(): boolean

Whether the receiver falls on today, tomorrow or yesterday. Only the date counts, so every type has them, Instant included. Today is read in the receiver's zone on a ZonedDateTime, otherwise in UTC, as in fromNow.

Chronos(Temporal.Now.plainDateISO("UTC")).isToday(); // true
Chronos(Temporal.Now.instant().add({ hours: 24 })).isTomorrow(); // true

Errors

All methods throw a TypeError if an argument is not of the receiver's type, and a RangeError if unit is not a unit, or one the receiver's type lacks.