diff --git a/src/typeEvaluator/functions.ts b/src/typeEvaluator/functions.ts
index 5d6f1e1..daaae63 100644
--- a/src/typeEvaluator/functions.ts
+++ b/src/typeEvaluator/functions.ts
@@ -2,7 +2,7 @@
 import type {FuncCallNode} from '../nodeTypes'
 import {Scope} from './scope'
 import {walk} from './typeEvaluate'
-import {mapConcrete} from './typeHelpers'
+import {mapConcrete, nullUnion} from './typeHelpers'
 import type {NullTypeNode, TypeNode} from './types'
 
 function unionWithoutNull(unionTypeNode: TypeNode): TypeNode {
@@ -148,6 +148,18 @@ export function handleFuncCallNode(node: FuncCallNode, scope: Scope): TypeNode {
       })
     }
 
+    case 'global.dateTime': {
+      const arg = walk({node: node.args[0], scope})
+
+      return mapConcrete(arg, scope, (arg) => {
+        if (arg.type === 'string') {
+          return nullUnion({type: 'string'}) // we don't know wether the string is a valid date or not, so we return a [null, string]-union
+        }
+
+        return {type: 'null'} satisfies NullTypeNode
+      })
+    }
+
     case 'global.references': {
       return {type: 'boolean'}
     }
diff --git a/test/typeEvaluate.test.ts b/test/typeEvaluate.test.ts
index f014e0c..f5da3fb 100644
--- a/test/typeEvaluate.test.ts
+++ b/test/typeEvaluate.test.ts
@@ -2230,6 +2230,57 @@ t.test('function: global::string', (t) => {
   t.end()
 })
 
+t.test('function: global::dateTime', (t) => {
+  const query = `*[_type == "author"] {
+    "string": dateTime(name),
+    "constant": dateTime("const"),
+    "number": dateTime(age),
+    "boolean": dateTime(true),
+    "object": dateTime(object)
+  }`
+  const ast = parse(query)
+  const res = typeEvaluate(ast, schemas)
+  t.strictSame(res, {
+    type: 'array',
+    of: {
+      type: 'object',
+      attributes: {
+        string: {
+          type: 'objectAttribute',
+          value: nullUnion({
+            type: 'string',
+          }),
+        },
+        constant: {
+          type: 'objectAttribute',
+          value: nullUnion({
+            type: 'string',
+          }),
+        },
+        number: {
+          type: 'objectAttribute',
+          value: {
+            type: 'null',
+          },
+        },
+        boolean: {
+          type: 'objectAttribute',
+          value: {
+            type: 'null',
+          },
+        },
+        object: {
+          type: 'objectAttribute',
+          value: {
+            type: 'null',
+          },
+        },
+      },
+    },
+  })
+  t.end()
+})
+
 t.test('function: global::upper', (t) => {
   const query = `*[_type == "author"] {
     "_type": upper(_type),
diff --git a/test/typeEvaluateCompare.test.ts b/test/typeEvaluateCompare.test.ts
index 6e94395..af66d33 100644
--- a/test/typeEvaluateCompare.test.ts
+++ b/test/typeEvaluateCompare.test.ts
@@ -424,6 +424,7 @@ const unaryFunctionTests: {namespace: string; funcName: string}[] = [
   {namespace: 'math', funcName: 'avg'},
   {namespace: 'array', funcName: 'compact'},
   {namespace: 'array', funcName: 'unique'},
+  {namespace: 'global', funcName: 'dateTime'},
 ]
 
 for (const {namespace, funcName} of unaryFunctionTests) {