1 | import type {
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2 | FirstWeekContainsDateOptions,
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3 | LocalizedOptions,
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4 | WeekOptions,
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5 | } from "./types.js";
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6 | /**
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7 | * The {@link startOfWeekYear} function options.
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8 | */
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9 | export interface StartOfWeekYearOptions
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10 | extends LocalizedOptions<"options">,
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11 | FirstWeekContainsDateOptions,
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12 | WeekOptions {}
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13 | /**
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14 | * @name startOfWeekYear
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15 | * @category Week-Numbering Year Helpers
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16 | * @summary Return the start of a local week-numbering year for the given date.
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17 | *
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18 | * @description
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19 | * Return the start of a local week-numbering year.
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20 | * The exact calculation depends on the values of
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21 | * `options.weekStartsOn` (which is the index of the first day of the week)
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22 | * and `options.firstWeekContainsDate` (which is the day of January, which is always in
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23 | * the first week of the week-numbering year)
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24 | *
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25 | * Week numbering: https://en.wikipedia.org/wiki/Week#The_ISO_week_date_system
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26 | *
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27 | * @typeParam DateType - The `Date` type, the function operates on. Gets inferred from passed arguments. Allows to use extensions like [`UTCDate`](https://github.com/date-fns/utc).
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28 | *
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29 | * @param date - The original date
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30 | * @param options - An object with options
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31 | *
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32 | * @returns The start of a week-numbering year
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33 | *
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34 | * @example
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35 | * // The start of an a week-numbering year for 2 July 2005 with default settings:
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36 | * const result = startOfWeekYear(new Date(2005, 6, 2))
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37 | * //=> Sun Dec 26 2004 00:00:00
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38 | *
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39 | * @example
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40 | * // The start of a week-numbering year for 2 July 2005
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41 | * // if Monday is the first day of week
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42 | * // and 4 January is always in the first week of the year:
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43 | * const result = startOfWeekYear(new Date(2005, 6, 2), {
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44 | * weekStartsOn: 1,
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45 | * firstWeekContainsDate: 4
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46 | * })
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47 | * //=> Mon Jan 03 2005 00:00:00
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48 | */
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49 | export declare function startOfWeekYear<DateType extends Date>(
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50 | date: DateType | number | string,
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51 | options?: StartOfWeekYearOptions,
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52 | ): DateType;
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