diff --git a/packages/core/src/utils/dateToLocaleISOString.newfoundland.spec.js b/packages/core/src/utils/dateToLocaleISOString.newfoundland.spec.js
index a2f1132c7a..0f783d687a 100644
--- a/packages/core/src/utils/dateToLocaleISOString.newfoundland.spec.js
+++ b/packages/core/src/utils/dateToLocaleISOString.newfoundland.spec.js
@@ -10,5 +10,5 @@ test('formatting a time in Cananda, Newfoundland timezone', () => {
   const date = new Date(Date.UTC(2000, 0, 1, 0, 12, 34, 567));
   const actual = dateToLocaleISOString(date);
 
-  expect(actual).toMatchInlineSnapshot(`"2000-01-01T09:12:34.567-03:30"`);
+  expect(actual).toMatchInlineSnapshot(`"1999-12-31T20:42:34.567-03:30"`);
 });
diff --git a/packages/core/src/utils/dateToLocaleISOString.ts b/packages/core/src/utils/dateToLocaleISOString.ts
index 25589d7e8e..3d3c7f16f0 100644
--- a/packages/core/src/utils/dateToLocaleISOString.ts
+++ b/packages/core/src/utils/dateToLocaleISOString.ts
@@ -45,9 +45,11 @@ export default function dateToLocaleISOString(date: Date): string {
   // "yyyy-MM-DDTHH:mm:ss.fff+08:00" for GMT+08
   // "yyyy-MM-DDTHH:mm:ss.fffZ" for UTC
 
+  const absoluteTimezoneOffset = ~~Math.abs(timezoneOffset);
+
   return `${date.getFullYear()}-${pad(date.getMonth() + 1)}-${pad(date.getDate())}T${pad(date.getHours())}:${pad(
     date.getMinutes()
   )}:${pad(date.getSeconds())}.${pad(date.getMilliseconds(), 3)}${
-    timezoneOffset ? `${timezoneSign}${pad(~~(Math.abs(timezoneOffset) / 60))}:${pad(timezoneOffset % 60)}` : 'Z'
+    timezoneOffset ? `${timezoneSign}${pad(~~(absoluteTimezoneOffset / 60))}:${pad(absoluteTimezoneOffset % 60)}` : 'Z'
   }`;
 }