diff --git a/src/dateutil.ts b/src/dateutil.ts
index b2cd176a..dc78be07 100644
--- a/src/dateutil.ts
+++ b/src/dateutil.ts
@@ -204,11 +204,13 @@ export const untilStringToDate = function (until: string) {
   )
 }
 
-const dateTZtoISO8601 = function (date: Date, timeZone: string) {
+export const dateTZtoISO8601 = function (date: Date, timeZone: string) {
   // date format for sv-SE is almost ISO8601
   const dateStr = date.toLocaleString('sv-SE', { timeZone })
   // '2023-02-07 10:41:36'
-  return dateStr.replace(' ', 'T') + 'Z'
+  return (
+    dateStr.replace('em', '').replace('fm', '').trim().replace(' ', 'T') + 'Z'
+  )
 }
 
 export const dateInTimeZone = function (date: Date, timeZone: string) {
diff --git a/test/dateutil.test.ts b/test/dateutil.test.ts
index b7787dd3..f673bf45 100644
--- a/test/dateutil.test.ts
+++ b/test/dateutil.test.ts
@@ -1,4 +1,4 @@
-import { datetime, untilStringToDate } from '../src/dateutil'
+import { datetime, untilStringToDate, dateTZtoISO8601 } from '../src/dateutil'
 
 describe('untilStringToDate', () => {
   it('parses a date string', () => {
@@ -6,3 +6,42 @@ describe('untilStringToDate', () => {
     expect(date.getTime()).toBe(datetime(1997, 9, 2, 9, 0, 0).getTime())
   })
 })
+
+describe('dateTZtoISO8601', () => {
+  it('correctly formats a date with em suffix from toLocaleString', () => {
+    // Mock Date.prototype.toLocaleString to simulate iOS behavior
+    const originalToLocaleString = Date.prototype.toLocaleString
+    Date.prototype.toLocaleString = jest.fn(() => '2045-10-31 1:00:00 em')
+
+    const date = new Date()
+    const timeZone = 'America/Los_Angeles'
+
+    // Your patched function that handles the iOS date string correctly
+    expect(dateTZtoISO8601(date, timeZone)).toBe('2045-10-31T1:00:00Z')
+
+    // Restore the original toLocaleString method after the test
+    Date.prototype.toLocaleString = originalToLocaleString
+  })
+
+  it('correctly formats a date with fm suffix from toLocaleString', () => {
+    // Mock Date.prototype.toLocaleString to simulate iOS behavior
+    const originalToLocaleString = Date.prototype.toLocaleString
+    Date.prototype.toLocaleString = jest.fn(() => '2045-10-31 1:00:00 fm')
+
+    const date = new Date()
+    const timeZone = 'America/Los_Angeles'
+
+    // Your patched function that handles the iOS date string correctly
+    expect(dateTZtoISO8601(date, timeZone)).toBe('2045-10-31T1:00:00Z')
+
+    // Restore the original toLocaleString method after the test
+    Date.prototype.toLocaleString = originalToLocaleString
+  })
+
+  it('formats a date in ISO8601 format for non-iOS environments', () => {
+    const date = new Date(1704830400000)
+    const timeZone = 'America/Los_Angeles'
+    // This tests the function in environments that do not have the ' em' issue
+    expect(dateTZtoISO8601(date, timeZone)).toBe('2024-01-09T12:00:00Z')
+  })
+})