diff --git a/backend/jest.config.js b/backend/jest.config.js
index d1cc7bd3f..a4a0ce1df 100644
--- a/backend/jest.config.js
+++ b/backend/jest.config.js
@@ -7,7 +7,8 @@ module.exports = {
     '!**/node_modules/**',
     '!**/test/**',
     '!**/build/**',
-    '!**/src/**/?(*.)+(spec|test).ts?(x)'
+    '!**/src/**/?(*.)+(spec|test).ts?(x)',
+    '!**/src/db/migrations/**'    
   ],
   coverageThreshold: {
     global: {
diff --git a/backend/src/db/migrations/20231017141022-fix-event-dates.ts b/backend/src/db/migrations/20231017141022-fix-event-dates.ts
new file mode 100644
index 000000000..3c4302f13
--- /dev/null
+++ b/backend/src/db/migrations/20231017141022-fix-event-dates.ts
@@ -0,0 +1,68 @@
+import { getDriver } from '../../db/neo4j'
+
+export const description = `
+Transform event start and end date of format 'YYYY-MM-DD HH:MM:SS' in CEST
+to ISOString in UTC.
+`
+
+export async function up(next) {
+  const driver = getDriver()
+  const session = driver.session()
+  const transaction = session.beginTransaction()
+
+  try {
+    const events = await transaction.run(`
+      MATCH (event:Event)
+      WHERE NOT event.eventStart CONTAINS 'T'
+      RETURN event.id, event.eventStart, event.eventEnd
+    `)
+    for (const event of events.records) {
+      let [id, eventStart, eventEnd] = event
+      let date = new Date(eventStart)
+      date.setHours(date.getHours() - 1)
+      eventStart = date.toISOString()
+      if (eventEnd) {
+        date = new Date(eventEnd)
+        date.setHours(date.getHours() - 1)
+        eventEnd = date.toISOString()
+      }
+      await transaction.run(`
+        MATCH (e:Event { id: '${id}' })
+        SET e.eventStart = '${eventStart}'
+        SET (CASE WHEN exists(e.eventEnd) THEN e END).eventEnd = '${eventEnd}'
+        RETURN e
+      `)
+    }
+    await transaction.commit()
+    next()
+  } catch (error) {
+    // eslint-disable-next-line no-console
+    console.log(error)
+    await transaction.rollback()
+    // eslint-disable-next-line no-console
+    console.log('rolled back')
+    throw new Error(error)
+  } finally {
+    session.close()
+  }
+}
+
+export async function down(next) {
+  const driver = getDriver()
+  const session = driver.session()
+  const transaction = session.beginTransaction()
+
+  try {
+    // No sense in running this down
+    next()
+  } catch (error) {
+    // eslint-disable-next-line no-console
+    console.log(error)
+    await transaction.rollback()
+    // eslint-disable-next-line no-console
+    console.log('rolled back')
+    throw new Error(error)
+  } finally {
+    session.close()
+  }
+}
diff --git a/backend/src/schema/resolvers/helpers/events.ts b/backend/src/schema/resolvers/helpers/events.ts
index 835088d8c..d4fc1fb11 100644
--- a/backend/src/schema/resolvers/helpers/events.ts
+++ b/backend/src/schema/resolvers/helpers/events.ts
@@ -34,6 +34,8 @@ const validateEventDate = (dateString) => {
   const date = new Date(dateString)
   if (date.toString() === 'Invalid Date')
     throw new UserInputError('Event start date must be a valid date!')
+  if (date.toISOString() !== dateString)
+    throw new UserInputError('Event start date must be in ISO format!')
   const now = new Date()
   if (date.getTime() < now.getTime()) {
     throw new UserInputError('Event start date must be in the future!')
@@ -44,6 +46,8 @@ const validateEventEnd = (start, end) => {
   const endDate = new Date(end)
   if (endDate.toString() === 'Invalid Date')
     throw new UserInputError('Event end date must be a valid date!')
+  if (endDate.toISOString() !== end)
+    throw new UserInputError('Event end date must be in ISO format!')
   const startDate = new Date(start)
   if (endDate < startDate)
     throw new UserInputError('Event end date must be a after event start date!')
diff --git a/backend/src/schema/resolvers/posts.spec.ts b/backend/src/schema/resolvers/posts.spec.ts
index 7a549449f..b816e25aa 100644
--- a/backend/src/schema/resolvers/posts.spec.ts
+++ b/backend/src/schema/resolvers/posts.spec.ts
@@ -374,6 +374,31 @@ describe('CreatePost', () => {
         })
       })
 
+      describe('with event start in no ISO format', () => {
+        it('throws an error', async () => {
+          const now = new Date()
+          const eventStart = new Date(now.getFullYear(), now.getMonth() - 1).toISOString()
+          await expect(
+            mutate({
+              mutation: createPostMutation(),
+              variables: {
+                ...variables,
+                postType: 'Event',
+                eventInput: {
+                  eventStart: eventStart.split('T')[0],
+                },
+              },
+            }),
+          ).resolves.toMatchObject({
+            errors: [
+              {
+                message: 'Event start date must be in ISO format!',
+              },
+            ],
+          })
+        })
+      })
+
       describe('with event start date in the past', () => {
         it('throws an error', async () => {
           const now = new Date()
@@ -423,6 +448,32 @@ describe('CreatePost', () => {
         })
       })
 
+      describe('with valid start date and not ISO formated end date', () => {
+        it('throws an error', async () => {
+          const now = new Date()
+          const eventEnd = new Date(now.getFullYear(), now.getMonth() + 2).toISOString()
+          await expect(
+            mutate({
+              mutation: createPostMutation(),
+              variables: {
+                ...variables,
+                postType: 'Event',
+                eventInput: {
+                  eventStart: new Date(now.getFullYear(), now.getMonth() + 1).toISOString(),
+                  eventEnd: eventEnd.split('T')[0],
+                },
+              },
+            }),
+          ).resolves.toMatchObject({
+            errors: [
+              {
+                message: 'Event end date must be in ISO format!',
+              },
+            ],
+          })
+        })
+      })
+
       describe('with valid start date and end date before start date', () => {
         it('throws an error', async () => {
           const now = new Date()
diff --git a/webapp/components/ContributionForm/ContributionForm.vue b/webapp/components/ContributionForm/ContributionForm.vue
index 0a5eba0cd..5af3d7a99 100644
--- a/webapp/components/ContributionForm/ContributionForm.vue
+++ b/webapp/components/ContributionForm/ContributionForm.vue
@@ -328,9 +328,9 @@ export default {
     eventInput() {
       if (this.createEvent) {
         return {
-          eventStart: this.formData.eventStart,
+          eventStart: new Date(this.formData.eventStart).toISOString(),
           eventVenue: this.formData.eventVenue,
-          eventEnd: this.formData.eventEnd,
+          eventEnd: this.formData.eventEnd ? new Date(this.formData.eventEnd).toISOString() : null,
           eventIsOnline: this.formData.eventIsOnline,
           eventLocationName: !this.formData.eventIsOnline ? this.formData.eventLocationName : null,
         }