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import toDate from '../toDate/index.ts'import requiredArgs from '../_lib/requiredArgs/index.ts'
/** * @name startOfDecade * @category Decade Helpers * @summary Return the start of a decade for the given date. * * @description * Return the start of a decade for the given date. * * ### v2.0.0 breaking changes: * * - [Changes that are common for the whole library](https://github.com/date-fns/date-fns/blob/master/docs/upgradeGuide.md#Common-Changes). * * @param {Date|Number} date - the original date * @returns {Date} the start of a decade * @throws {TypeError} 1 argument required * * @example * // The start of a decade for 21 October 2015 00:00:00: * const result = startOfDecade(new Date(2015, 9, 21, 00, 00, 00)) * //=> Jan 01 2010 00:00:00 */export default function startOfDecade(dirtyDate: Date | number): Date {  requiredArgs(1, arguments)
  const date = toDate(dirtyDate)  const year = date.getFullYear()  const decade = Math.floor(year / 10) * 10  date.setFullYear(decade, 0, 1)  date.setHours(0, 0, 0, 0)  return date}