Initial fix for merge conflicts (will rebase soon)

polyfill/lib/date.mjs

@@ -125,12 +125,13 @@ export class Date {
   difference(other, options) {
     if (!ES.IsTemporalDate(this)) throw new TypeError('invalid receiver');
     if (!ES.IsTemporalDate(other)) throw new TypeError('invalid Date object');
-    const largestUnit = ES.ToLargestTemporalUnit(options, 'days', ['hours', 'minutes', 'seconds']);
+    const calendar = GetSlot(this, CALENDAR);
+    if (calendar.id !== GetSlot(other, CALENDAR).id) {
+      other = new Date(GetSlot(other, ISO_YEAR), GetSlot(other, ISO_MONTH), GetSlot(other, ISO_DAY), calendar);
+    }
     const comparison = Date.compare(this, other);
     if (comparison < 0) throw new RangeError('other instance cannot be larger than `this`');
-    const { years, months, weeks, days } = ES.DifferenceDate(other, this, largestUnit);
-    const Duration = GetIntrinsic('%Temporal.Duration%');
-    return new Duration(years, months, weeks, days, 0, 0, 0, 0, 0, 0);
+    return calendar.difference(other, this, options);
   }
   equals(other) {
     if (!ES.IsTemporalDate(this)) throw new TypeError('invalid receiver');

polyfill/lib/datetime.mjs

@@ -245,17 +245,17 @@ export class DateTime {
       other,
       this
     );
-    let { year, month, day } = this;
-    day += deltaDays;
+    let year = GetSlot(larger, ISO_YEAR);
+    let month = GetSlot(larger, ISO_MONTH);
+    let day = GetSlot(larger, ISO_DAY) + deltaDays;
     ({ year, month, day } = ES.BalanceDate(year, month, day));
 
     let dateLargestUnit = 'days';
     if (largestUnit === 'years' || largestUnit === 'months' || largestUnit === 'weeks') {
       dateLargestUnit = largestUnit;
     }
 
-    let { years, months, weeks, days } = ES.DifferenceDate(other, { year, month, day }, dateLargestUnit);
-
+    let days;
     ({ days, hours, minutes, seconds, milliseconds, microseconds, nanoseconds } = ES.BalanceDuration(
       days,
       hours,

polyfill/lib/yearmonth.mjs

@@ -102,18 +102,13 @@ export class YearMonth {
     const largestUnit = ES.ToLargestTemporalUnit(options, 'years', ['weeks', 'days', 'hours', 'minutes', 'seconds']);
     const comparison = YearMonth.compare(this, other);
     if (comparison < 0) throw new RangeError('other instance cannot be larger than `this`');
-    let years = this.year - other.year;
-    let months = this.month - other.month;
-    if (months < 0) {
-      years -= 1;
-      months += 12;
-    }
-    if (largestUnit === 'months') {
-      months += 12 * years;
-      years = 0;
-    }
-    const Duration = GetIntrinsic('%Temporal.Duration%');
-    return new Duration(years, months);
+
+    const smallerFields = ES.ToTemporalYearMonthRecord(other);
+    const largerFields = ES.ToTemporalYearMonthRecord(this);
+    const TemporalDate = GetIntrinsic('%Temporal.Date%');
+    const smaller = calendar.dateFromFields({ ...smallerFields, day: 1 }, {}, TemporalDate);
+    const larger = calendar.dateFromFields({ ...largerFields, day: 1 }, {}, TemporalDate);
+    return calendar.difference(smaller, larger, { ...options, largestUnit });
   }
   equals(other) {
     if (!ES.IsTemporalYearMonth(this)) throw new TypeError('invalid receiver');