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+/* eslint-env mocha */
+
+import assert from 'power-assert'
+import differenceInDays from '.'
+import { getDstTransitions } from '../../test/dst/tzOffsetTransitions'
+
+describe('differenceInDays', function () {
+ it('returns the number of full days between the given dates', function () {
+ const result = differenceInDays(
+ new Date(2012, 6 /* Jul */, 2, 18, 0),
+ new Date(2011, 6 /* Jul */, 2, 6, 0)
+ )
+ assert(result === 366)
+ })
+
+ it('returns a negative number if the time value of the first date is smaller', function () {
+ const result = differenceInDays(
+ new Date(2011, 6 /* Jul */, 2, 6, 0),
+ new Date(2012, 6 /* Jul */, 2, 18, 0)
+ )
+ assert(result === -366)
+ })
+
+ it('accepts timestamps', function () {
+ const result = differenceInDays(
+ new Date(2014, 8 /* Sep */, 5, 18, 0).getTime(),
+ new Date(2014, 8 /* Sep */, 4, 6, 0).getTime()
+ )
+ assert(result === 1)
+ })
+
+ describe('edge cases', function () {
+ it('the difference is less than a day, but the given dates are in different calendar days', function () {
+ const result = differenceInDays(
+ new Date(2014, 8 /* Sep */, 5, 0, 0),
+ new Date(2014, 8 /* Sep */, 4, 23, 59)
+ )
+ assert(result === 0)
+ })
+
+ it('the same for the swapped dates', function () {
+ const result = differenceInDays(
+ new Date(2014, 8 /* Sep */, 4, 23, 59),
+ new Date(2014, 8 /* Sep */, 5, 0, 0)
+ )
+ assert(result === 0)
+ })
+
+ it('the time values of the given dates are the same', function () {
+ const result = differenceInDays(
+ new Date(2014, 8 /* Sep */, 6, 0, 0),
+ new Date(2014, 8 /* Sep */, 5, 0, 0)
+ )
+ assert(result === 1)
+ })
+
+ it('the given dates are the same', function () {
+ const result = differenceInDays(
+ new Date(2014, 8 /* Sep */, 5, 0, 0),
+ new Date(2014, 8 /* Sep */, 5, 0, 0)
+ )
+ assert(result === 0)
+ })
+
+ const dstTransitions = getDstTransitions(2017)
+ const dstOnly = dstTransitions.start && dstTransitions.end ? it : it.skip
+ const tz =
+ Intl.DateTimeFormat().resolvedOptions().timeZone || process.env.tz
+ dstOnly(
+ `works across DST start & end in local timezone: ${tz || '(unknown)'}`,
+ function () {
+ const { start, end } = dstTransitions
+ const HOUR = 1000 * 60 * 60
+ const MINUTE = 1000 * 60
+ function sameTime(t1: Date, t2: Date): boolean {
+ return (
+ t1.getHours() === t2.getHours() &&
+ t1.getMinutes() === t2.getMinutes() &&
+ t1.getSeconds() === t2.getSeconds() &&
+ t1.getMilliseconds() === t2.getMilliseconds()
+ )
+ }
+
+ assert(start !== undefined)
+ assert(end !== undefined)
+
+ if (start === undefined || end === undefined) {
+ return
+ }
+
+ // It's usually 1 hour, but for some timezones, e.g. Australia/Lord_Howe, it is 30 minutes
+ const dstOffset =
+ (end.getTimezoneOffset() - start.getTimezoneOffset()) * MINUTE
+
+ // TEST DST START (SPRING)
+
+ // anchor to one hour before the boundary
+ {
+ const a = new Date(start.getTime() - HOUR) // 1 hour before DST
+ const b = new Date(a.getTime() + 24 * HOUR - dstOffset) // 1 day later, same local time
+ const c = new Date(a.getTime() + 48 * HOUR - dstOffset) // 2 days later, same local time
+
+ assert(sameTime(a, b))
+ assert(sameTime(a, c))
+ assert(sameTime(b, c))
+ assert(differenceInDays(c, b) === 1) // normal 24-hour day
+ assert(differenceInDays(b, a) === 1) // 23 hours -> 1 day
+ assert(differenceInDays(c, a) === 2) // 47 hours -> 2 days
+ }
+ // anchor exactly, the boundary
+ {
+ const a = start // exactly when DST starts
+ const b = new Date(a.getTime() + 24 * HOUR) // 1 day later, same local time
+ const c = new Date(a.getTime() + 48 * HOUR) // 2 days later, same local time
+
+ assert(sameTime(a, b))
+ assert(sameTime(a, c))
+ assert(sameTime(b, c))
+ assert(differenceInDays(c, b) === 1) // normal 24-hour day
+ assert(differenceInDays(b, a) === 1) // normal 24-hour day
+ assert(differenceInDays(c, a) === 2) // 2 normal 24-hour days
+ }
+
+ // TEST DST END (FALL)
+
+ // make sure that diffs across a "fall back" DST boundary won't report a full day
+ // until 25 hours have elapsed.
+ {
+ const a = new Date(end.getTime() - HOUR / 2) // 1 hour before Standard Time starts
+ const b = new Date(a.getTime() + 24 * HOUR + dstOffset - 15 * MINUTE) // 1 day later, 15 mins earlier local time
+ const c = new Date(a.getTime() + 48 * HOUR + dstOffset - 15 * MINUTE) // 2 days later, 15 mins earlier local time
+
+ assert(differenceInDays(c, b) === 1) // normal 24-hour day
+ assert(differenceInDays(b, a) === 0) // 24.75 hours -> 0 full days (because hour lost to DST)
+ assert(differenceInDays(c, a) === 1) // 48.75 hours -> 1 full day (because hour lost to DST)
+ }
+ // anchor to one hour before the boundary
+ {
+ const a = new Date(end.getTime() - HOUR) // 1 hour before Standard Time start
+ const b = new Date(a.getTime() + 24 * HOUR + dstOffset) // 1 day later, same local time
+ const c = new Date(a.getTime() + 48 * HOUR + dstOffset) // 2 days later, same local time
+
+ assert(sameTime(a, b))
+ assert(sameTime(a, c))
+ assert(sameTime(b, c))
+ assert(differenceInDays(c, b) === 1) // normal 24-hour day
+ assert(differenceInDays(b, a) === 1) // 25 hours -> 1 day
+ assert(differenceInDays(c, a) === 2) // 49 hours -> 2 days
+ }
+ // anchor to one hour after the boundary
+ {
+ const a = new Date(end.getTime() + HOUR) // 1 hour after Standard Time start
+ const b = new Date(a.getTime() + 24 * HOUR) // 1 day later, same local time
+ const c = new Date(a.getTime() + 48 * HOUR) // 2 days later, same local time
+
+ assert(sameTime(a, b))
+ assert(sameTime(a, c))
+ assert(sameTime(b, c))
+ assert(differenceInDays(c, b) === 1) // normal 24-hour day
+ assert(differenceInDays(b, a) === 1) // normal 24-hour day
+ assert(differenceInDays(c, a) === 2) // 2 normal 24-hour days
+ }
+ // anchor exactly at the boundary
+ {
+ const a = end // exactly when Standard Time starts
+ const b = new Date(a.getTime() + 24 * HOUR) // 1 day later, same local time
+ const c = new Date(a.getTime() + 48 * HOUR) // 2 days later, same local time
+ assert(differenceInDays(b, a) === 1) // normal 24-hour day
+ assert(differenceInDays(c, a) === 2) // 2 normal 24-hour days
+ }
+ }
+ )
+
+ it('does not return -0 when the given dates are the same', () => {
+ function isNegativeZero(x: number): boolean {
+ return x === 0 && 1 / x < 0
+ }
+
+ const result = differenceInDays(
+ new Date(2014, 8 /* Sep */, 5, 0, 0),
+ new Date(2014, 8 /* Sep */, 5, 0, 0)
+ )
+
+ const resultIsNegative = isNegativeZero(result)
+ assert(resultIsNegative === false)
+ })
+ })
+
+ it('returns NaN if the first date is `Invalid Date`', function () {
+ const result = differenceInDays(
+ new Date(NaN),
+ new Date(2017, 0 /* Jan */, 1)
+ )
+ assert(isNaN(result))
+ })
+
+ it('returns NaN if the second date is `Invalid Date`', function () {
+ const result = differenceInDays(
+ new Date(2017, 0 /* Jan */, 1),
+ new Date(NaN)
+ )
+ assert(isNaN(result))
+ })
+
+ it('returns NaN if the both dates are `Invalid Date`', function () {
+ const result = differenceInDays(new Date(NaN), new Date(NaN))
+ assert(isNaN(result))
+ })
+
+ it('throws TypeError exception if passed less than 2 arguments', function () {
+ assert.throws(differenceInDays.bind(null), TypeError)
+ assert.throws(differenceInDays.bind(null, 1), TypeError)
+ })
+})
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