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42 lines
1.4 KiB
42 lines
1.4 KiB
4 years ago
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var startOfDay = require('../start_of_day/index.js')
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var MILLISECONDS_IN_MINUTE = 60000
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var MILLISECONDS_IN_DAY = 86400000
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/**
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* @category Day Helpers
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* @summary Get the number of calendar days between the given dates.
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*
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* @description
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* Get the number of calendar days between the given dates.
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*
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* @param {Date|String|Number} dateLeft - the later date
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* @param {Date|String|Number} dateRight - the earlier date
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* @returns {Number} the number of calendar days
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*
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* @example
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* // How many calendar days are between
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* // 2 July 2011 23:00:00 and 2 July 2012 00:00:00?
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* var result = differenceInCalendarDays(
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* new Date(2012, 6, 2, 0, 0),
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* new Date(2011, 6, 2, 23, 0)
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* )
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* //=> 366
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*/
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function differenceInCalendarDays (dirtyDateLeft, dirtyDateRight) {
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var startOfDayLeft = startOfDay(dirtyDateLeft)
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var startOfDayRight = startOfDay(dirtyDateRight)
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var timestampLeft = startOfDayLeft.getTime() -
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startOfDayLeft.getTimezoneOffset() * MILLISECONDS_IN_MINUTE
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var timestampRight = startOfDayRight.getTime() -
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startOfDayRight.getTimezoneOffset() * MILLISECONDS_IN_MINUTE
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// Round the number of days to the nearest integer
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// because the number of milliseconds in a day is not constant
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// (e.g. it's different in the day of the daylight saving time clock shift)
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return Math.round((timestampLeft - timestampRight) / MILLISECONDS_IN_DAY)
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}
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module.exports = differenceInCalendarDays
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