fix: incorrect timezone correction for DST dates, fixes #604

src/util/liquid-date.ts

@@ -14,6 +14,6 @@ export interface LiquidDate {
   getMonth(): number;
   getFullYear(): number;
   getTimezoneOffset(): number;
-  toLocaleTimeString(locale?: string, init?: any): string;
-  toLocaleDateString(locale?: string, init?: any): string;
+  toLocaleTimeString(): string;
+  toLocaleDateString(): string;
 }

src/util/timezone-date.spec.ts

@@ -24,6 +24,12 @@ describe('TimezoneDate', () => {
     const date = new TimezoneDate('2021-12-07T00:00:00.001+08:00', -480)
     expect(date.getDay()).toBe(2)
   })
+  it('should support .toLocaleString()', () => {
+    const date = new TimezoneDate('2021-10-06T00:00:00.001+00:00', -480)
+    expect(date.toLocaleString('en-US')).toMatch(/8:00:00\sAM$/)
+    expect(date.toLocaleString('en-US', { timeZone: 'America/New_York' })).toMatch(/8:00:00\sPM$/)
+    expect(() => date.toLocaleString()).not.toThrow()
+  })
   it('should support .toLocaleTimeString()', () => {
     const date = new TimezoneDate('2021-10-06T00:00:00.001+00:00', -480)
     expect(date.toLocaleTimeString('en-US')).toMatch(/^8:00:00\sAM$/)

src/util/timezone-date.ts

@@ -2,7 +2,6 @@ import { LiquidDate } from './liquid-date'
 
 // one minute in milliseconds
 const OneMinute = 60000
-const hostTimezoneOffset = new Date().getTimezoneOffset()
 const ISO8601_TIMEZONE_PATTERN = /([zZ]|([+-])(\d{2}):(\d{2}))$/
 
 /**
@@ -22,7 +21,7 @@ export class TimezoneDate implements LiquidDate {
       : new Date(init)
     this.timezoneOffset = timezoneOffset
 
-    const diff = (hostTimezoneOffset - this.timezoneOffset) * OneMinute
+    const diff = (this.date.getTimezoneOffset() - this.timezoneOffset) * OneMinute
     const time = this.date.getTime() + diff
     this.displayDate = new Date(time)
   }
@@ -56,22 +55,16 @@ export class TimezoneDate implements LiquidDate {
     return this.displayDate.getFullYear()
   }
   toLocaleString (locale?: string, init?: any) {
-    if (locale === undefined) {
-      return this.displayDate.toLocaleString(locale)
+    if (init?.timeZone) {
+      return this.date.toLocaleString(locale, init)
     }
-    return this.date.toLocaleString(locale, init)
+    return this.displayDate.toLocaleString(locale, init)
   }
-  toLocaleTimeString (locale?: string, init?: any) {
-    if (locale === undefined) {
-      return this.displayDate.toLocaleTimeString(locale)
-    }
-    return this.date.toLocaleTimeString(locale, init)
+  toLocaleTimeString (locale?: string) {
+    return this.displayDate.toLocaleTimeString(locale)
   }
-  toLocaleDateString (locale?: string, init?: any) {
-    if (locale === undefined) {
-      return this.displayDate.toLocaleDateString(locale)
-    }
-    return this.date.toLocaleDateString(locale, init)
+  toLocaleDateString (locale?: string) {
+    return this.displayDate.toLocaleDateString(locale)
   }
   getTimezoneOffset () {
     return this.timezoneOffset!