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A Iso.YearMonth represents a particular month on the calendar. For example, it could be used to represent a particular instance of a monthly recurring event, like "the June 2019 meeting".

Iso.YearMonth refers to the whole of a specific month; if you need to refer to a calendar event on a certain day, use Iso.Date or even Iso.DateTime. A Iso.YearMonth can be converted into a Iso.Date by combining it with a day of the month, using the toDate() function.

fromNumbers()​

fromNumbers(year, month): YearMonth

Parameters​

year​

number

month​

number

Returns​

YearMonth

isValid()​

isValid(yearMonth): yearMonth is YearMonth

Parameters​

yearMonth​

unknown

Returns​

yearMonth is YearMonth

assertIsValid()​

assertIsValid(yearMonth): asserts yearMonth is YearMonth

Parameters​

yearMonth​

unknown

Returns​

asserts yearMonth is YearMonth

getYear()​

getYear(yearMonth): number

Parameters​

yearMonth​

YearMonth

Returns​

number

getMonth()​

getMonth(yearMonth): number

Parameters​

yearMonth​

YearMonth

Returns​

number

getDaysInMonth()​

getDaysInMonth(yearMonth): number

Parameters​

yearMonth​

YearMonth

Returns​

number

getDaysInYear()​

getDaysInYear(yearMonth): number

Parameters​

yearMonth​

YearMonth

Returns​

number

inLeapYear()​

inLeapYear(yearMonth): boolean

Parameters​

yearMonth​

YearMonth

Returns​

boolean

with()​

with(yearMonth, yearMonthLike, options?): YearMonth

Parameters​

yearMonth​

YearMonth

yearMonthLike​

year?​

number

month?​

number

options?​

overflow​

"constrain" | "reject"

Returns​

YearMonth

add()​

add(yearMonth, temporalDurationLike, options?): YearMonth

Parameters​

yearMonth​

YearMonth

temporalDurationLike​

Duration | { years?: number; months?: number; weeks?: number; days?: number; hours?: number; minutes?: number; seconds?: number; milliseconds?: number; }

options?​

overflow?​

"constrain" | "reject"

Returns​

YearMonth

subtract()​

subtract(yearMonth, temporalDurationLike, options?): YearMonth

Parameters​

yearMonth​

YearMonth

temporalDurationLike​

Duration | { years?: number; months?: number; weeks?: number; days?: number; hours?: number; minutes?: number; seconds?: number; milliseconds?: number; }

options?​

overflow?​

"constrain" | "reject"

Returns​

YearMonth

until()​

until(yearMonth, other, options?): Duration

Parameters​

yearMonth​

YearMonth

other​

YearMonth

options?​

largestUnit?​

LargestUnit\<"month" | "year">

smallestUnit?​

SmallestUnit\<"month" | "year">

roundingIncrement?​

number

roundingMode?​

RoundingMode

Returns​

Duration

since()​

since(yearMonth, other, options?): Duration

Parameters​

yearMonth​

YearMonth

other​

YearMonth

options?​

largestUnit?​

LargestUnit\<"month" | "year">

smallestUnit?​

SmallestUnit\<"month" | "year">

roundingIncrement?​

number

roundingMode?​

RoundingMode

Returns​

Duration

equals()​

equals(yearMonth, other): boolean

Parameters​

yearMonth​

YearMonth

other​

YearMonth

Returns​

boolean

isEqual()​

isEqual(yearMonth, other): boolean

alias for equals

Parameters​

yearMonth​

YearMonth

other​

YearMonth

Returns​

boolean

isBefore()​

isBefore(yearMonth, other): boolean

Parameters​

yearMonth​

YearMonth

other​

YearMonth

Returns​

boolean

isAfter()​

isAfter(yearMonth, other): boolean

Parameters​

yearMonth​

YearMonth

other​

YearMonth

Returns​

boolean

isEqualOrBefore()​

isEqualOrBefore(yearMonth, other): boolean

Parameters​

yearMonth​

YearMonth

other​

YearMonth

Returns​

boolean

isEqualOrAfter()​

isEqualOrAfter(yearMonth, other): boolean

Parameters​

yearMonth​

YearMonth

other​

YearMonth

Returns​

boolean

toDate()​

toDate(yearMonth, day): Date

Parameters​

yearMonth​

YearMonth

day​

number

Returns​

Date

getFields()​

getFields(yearMonth): YearMonthSlots

Parameters​

yearMonth​

YearMonth

Returns​

YearMonthSlots

from()​

from(item, options?): YearMonth

Parameters​

item​

string | Partial\<YearMonthSlots>

options?​

overflow​

"constrain" | "reject"

Returns​

YearMonth

compare()​

compare(one, two): number

Parameters​

one​

YearMonth

two​

YearMonth

Returns​

number

format()​

format(yearMonth, format, options?): string

Parameters​

yearMonth​

YearMonth

the original date

format​

string

the string of tokens

options?​

FormatOptions

Returns​

string

the formatted date string

Description​

Return the formatted ZonedDateTime string in the given format.

The characters wrapped between two single quotes characters (') are escaped. Two single quotes in a row, whether inside or outside a quoted sequence, represent a 'real' single quote. (see the last example)

Format of the string is based on Unicode Technical Standard #35: https://www.unicode.org/reports/tr35/tr35-dates.html#Date_Field_Symbol_Table with a few additions (see note 7 below the table).

Accepted patterns:

UnitPatternResult examplesNotes
EraG..GGGAD, BC
GGGGAnno Domini, Before Christ1
GGGGGA, B
Calendar yeary44, 1, 1900, 20174
yo44th, 1st, 0th, 17th4,5
yy44, 01, 00, 174
yyy044, 001, 1900, 20174
yyyy0044, 0001, 1900, 20174
yyyyy...2,4
Extended yearu-43, 0, 1, 1900, 20174
uu-43, 01, 1900, 20174
uuu-043, 001, 1900, 20174
uuuu-0043, 0001, 1900, 20174
uuuuu...2,4
QuarterQ1, 2, 3, 4
Qo1st, 2nd, 3rd, 4th5
QQ01, 02, 03, 04
QQQQ1, Q2, Q3, Q4
QQQQ1st quarter, 2nd quarter, ...1
QQQQQ1, 2, 3, 43
MonthM1, 2, ..., 12
Mo1st, 2nd, ..., 12th5
MM01, 02, ..., 12
MMMJan, Feb, ..., Dec
MMMMJanuary, February, ..., December1
MMMMMJ, F, ..., D

Notes:

  1. Any sequence of the identical letters is a pattern, unless it is escaped by the single quote characters (see below). If the sequence is longer than listed in table (e.g. EEEEEEEEEEE) the output will be the same as default pattern for this unit, usually the longest one (in case of ISO weekdays, EEEE). Default patterns for units are marked with "2" in the last column of the table.

    format("2017-11-06", 'MMM') //=> 'Nov'

    format("2017-11-06", 'MMMM') //=> 'November'

    format("2017-11-06", 'MMMMM') //=> 'N'

    format("2017-11-06", 'MMMMMM') //=> 'November'

    format("2017-11-06", 'MMMMMMM') //=> 'November'

  2. Some patterns could be unlimited length (such as yyyyyyyy). The output will be padded with zeros to match the length of the pattern.

    format("2017-11-06", 'yyyyyyyy') //=> '00002017'

  3. QQQQQ could be not strictly numerical in some locales. These tokens represent the shortest form of the quarter.

  4. The main difference between y and u patterns are B.C. years:

    Yearyu
    AC 111
    BC 110
    BC 22-1

    Also yy always returns the last two digits of a year, while uu pads single digit years to 2 characters and returns other years unchanged:

    Yearyyuu
    10101
    141414
    37676376
    1453531453

  5. These patterns are not in the Unicode Technical Standard #35:

    • o: ordinal number modifier
  • Characters are escaped using single quote symbols (').

Example​

// Represent 11 February 2014 in middle-endian format:
var result = format("2014-02", 'MM/yyyy')
//=> '02/2014'

chain()​

chain(yearMonth): IYearMonthChain

Parameters​

yearMonth​

YearMonth

Returns​

IYearMonthChain