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