diff --git a/packages/@sanity/mutator/src/document/Mutation.ts b/packages/@sanity/mutator/src/document/Mutation.ts
index 0d04d187750..ad145532652 100644
--- a/packages/@sanity/mutator/src/document/Mutation.ts
+++ b/packages/@sanity/mutator/src/document/Mutation.ts
@@ -106,17 +106,21 @@ export class Mutation {
   compile(): void {
     const operations: ((doc: Doc | null) => Doc | null)[] = []
 
+    // creation requires a _createdAt
+    const getGuaranteedCreatedAt = (doc: Doc): string =>
+      doc?._createdAt || this.params.timestamp || new Date().toISOString()
+
     this.mutations.forEach((mutation) => {
       if (mutation.create) {
         // TODO: Fail entire patch if document did exist
-        const create = mutation.create || {}
+        const create = (mutation.create || {}) as Doc
         operations.push((doc): Doc => {
           if (doc) {
             return doc
           }
 
-          return Object.assign(create as Doc, {
-            _createdAt: create._createdAt || this.params.timestamp,
+          return Object.assign(create, {
+            _createdAt: getGuaranteedCreatedAt(create),
           })
         })
         return
@@ -127,7 +131,7 @@ export class Mutation {
         operations.push((doc) =>
           doc === null
             ? Object.assign(createIfNotExists, {
-                _createdAt: createIfNotExists._createdAt || this.params.timestamp,
+                _createdAt: getGuaranteedCreatedAt(createIfNotExists),
               })
             : doc,
         )
@@ -138,7 +142,7 @@ export class Mutation {
         const createOrReplace = mutation.createOrReplace || {}
         operations.push(() =>
           Object.assign(createOrReplace, {
-            _createdAt: createOrReplace._createdAt || this.params.timestamp,
+            _createdAt: getGuaranteedCreatedAt(createOrReplace),
           }),
         )
         return
diff --git a/packages/@sanity/mutator/src/document/types.ts b/packages/@sanity/mutator/src/document/types.ts
index acd147e4b7d..215cf2c67d2 100644
--- a/packages/@sanity/mutator/src/document/types.ts
+++ b/packages/@sanity/mutator/src/document/types.ts
@@ -16,6 +16,7 @@ export interface Doc {
   _type: string
   _rev?: string
   _updatedAt?: string
+  _createdAt?: string
   [attribute: string]: unknown
 }
 
diff --git a/packages/@sanity/mutator/test/SquashingBuffer.test.ts b/packages/@sanity/mutator/test/SquashingBuffer.test.ts
index ab5ee308a59..6544bddf769 100644
--- a/packages/@sanity/mutator/test/SquashingBuffer.test.ts
+++ b/packages/@sanity/mutator/test/SquashingBuffer.test.ts
@@ -1,4 +1,4 @@
-import {expect, test} from '@jest/globals'
+import {expect, jest, test} from '@jest/globals'
 import {type PatchMutationOperation} from '@sanity/types'
 
 import {Mutation} from '../src/document/Mutation'
@@ -109,7 +109,39 @@ test('de-duplicate createIfNotExists', () => {
   expect(tx2 && tx2.mutations.length).toBe(1)
 })
 
+test.each(['create', 'createIfNotExists', 'createOrReplace'])(
+  '%s defaults to current created at time',
+  (createFnc) => {
+    const globalMockDate = new Date('2020-01-01T12:34:55.000Z')
+    const globalDateSpy = jest.spyOn(global, 'Date').mockReturnValue(globalMockDate)
+
+    const sb = new SquashingBuffer(null)
+
+    add(sb, {[createFnc]: {_id: '1', _type: 'test', a: 'A string value'}})
+
+    const tx = sb.purge('txn_id')
+    if (!tx) {
+      throw new Error('buffer purge did not result in a mutation')
+    }
+
+    const final = tx.apply(null)
+
+    expect(final).toEqual({
+      _id: '1',
+      _rev: 'txn_id',
+      _createdAt: '2020-01-01T12:34:55.000Z',
+      _type: 'test',
+      a: 'A string value',
+    })
+
+    globalDateSpy.mockRestore()
+  },
+)
+
 test('de-duplicate create respects deletes', () => {
+  const globalMockDate = new Date('2020-01-01T12:34:55.000Z')
+  const globalDateSpy = jest.spyOn(global, 'Date').mockReturnValue(globalMockDate)
+
   const initial = {_id: '1', _type: 'test', a: 'A string value', c: 'Some value'}
   const sb = new SquashingBuffer(initial)
   add(sb, {createIfNotExists: {_id: '1', _type: 'test', a: 'A string value', c: 'Some value'}})
@@ -124,7 +156,7 @@ test('de-duplicate create respects deletes', () => {
   if (!tx) {
     throw new Error('buffer purge did not result in a mutation')
   }
-  tx.params.timestamp = '2021-01-01T12:34:55Z'
+  tx.params.timestamp = '2021-01-01T12:34:55.000Z'
 
   const creates = tx.mutations.filter((mut) => !!mut.createIfNotExists)
   expect(creates.length).toBe(2) // Only a single create mutation expected (note: bn - is this correct?)
@@ -134,14 +166,16 @@ test('de-duplicate create respects deletes', () => {
   expect(final).toEqual({
     _id: '1',
     _type: 'test',
-    _createdAt: '2021-01-01T12:34:55Z',
-    _updatedAt: '2021-01-01T12:34:55Z',
+    _createdAt: '2020-01-01T12:34:55.000Z',
+    _updatedAt: '2021-01-01T12:34:55.000Z',
     _rev: 'txn_id',
     a: {
       b: 'A wrapped value',
     },
     c: 'Changed',
   })
+
+  globalDateSpy.mockRestore()
 })
 
 test('de-duplicate create respects rebasing', () => {