The earlier date
Optionaloptions: DifferenceInWeeksOptionsAn object with options
The number of full weeks
Get the number of full weeks between two dates. Fractional weeks are truncated towards zero by default.
One "full week" is the distance between a local time in one day to the same local time 7 days earlier or later. A full week can sometimes be less than or more than 7*24 hours if a daylight savings change happens between two dates.
To ignore DST and only measure exact 7*24-hour periods, use this instead:
Math.trunc(differenceInHours(dateLeft, dateRight)/(7*24))|0.
// How many full weeks are between 5 July 2014 and 20 July 2014?
const result = differenceInWeeks(new Date(2014, 6, 20), new Date(2014, 6, 5))
//=> 2
// How many full weeks are between
// 1 March 2020 0:00 and 6 June 2020 0:00 ?
// Note: because local time is used, the
// result will always be 8 weeks (54 days),
// even if DST starts and the period has
// only 54*24-1 hours.
const result = differenceInWeeks(
new Date(2020, 5, 1),
new Date(2020, 2, 6)
)
//=> 8
The later date