diff --git a/README.md b/README.md
index 9a4d1e9..ee6e98e 100644
--- a/README.md
+++ b/README.md
@@ -71,6 +71,29 @@ api.Walk(func(path string, endpoint *swagger.Endpoint) {
 })
 ```
 
+### Custom Types
+
+For types implementing `json.Marshaler` whose JSON output does not match their Go types (such as `time.Time`),
+it is possible to override the default scanning of types and define a property manually.
+
+For example:
+
+```go
+type Person struct {
+  Name string `json:"name"`
+  Birthday time.Time `json:"birthday"`
+}
+
+func main() {
+  RegisterCustomType(time.Time{}, Property{
+    Type: "string",
+    Format: "date-time",
+  })
+}
+```
+
+`time.Time` is automatically registered as a custom type.
+
 ## Complete Example
 
 ```go
diff --git a/examples/builtin/main.go b/examples/builtin/main.go
index c762704..0403db4 100644
--- a/examples/builtin/main.go
+++ b/examples/builtin/main.go
@@ -3,6 +3,7 @@ package main
 import (
 	"io"
 	"net/http"
+	"time"
 
 	"github.com/savaki/swag"
 	"github.com/savaki/swag/endpoint"
@@ -20,11 +21,13 @@ type Category struct {
 
 // Pet example from the swagger pet store
 type Pet struct {
-	ID        int64    `json:"id"`
-	Category  Category `json:"category"`
-	Name      string   `json:"name"`
-	PhotoUrls []string `json:"photoUrls"`
-	Tags      []string `json:"tags"`
+	ID        int64      `json:"id"`
+	Category  Category   `json:"category"`
+	Name      string     `json:"name"`
+	PhotoUrls []string   `json:"photoUrls"`
+	Tags      []string   `json:"tags"`
+	CreatedAt time.Time  `json:"createdAt"`
+	DeletedAt *time.Time `json:"deletedAt"`
 }
 
 func main() {
diff --git a/swagger/reflect.go b/swagger/reflect.go
index aeffec1..1cf74e3 100644
--- a/swagger/reflect.go
+++ b/swagger/reflect.go
@@ -3,9 +3,52 @@ package swagger
 import (
 	"reflect"
 	"strings"
+	"time"
 )
 
+var customTypes map[reflect.Type]Property
+
+func init() {
+	customTypes = map[reflect.Type]Property{}
+
+	RegisterCustomType(time.Time{}, Property{
+		Type:   "string",
+		Format: "date-time",
+	})
+}
+
+// RegisterCustomType maps a reflect.Type to a pre-defined Property. This can be
+// used to handle types that implement json.Marshaler or other interfaces.
+// For example, a property with a Go type of time.Time would be represented as
+// an object when it should be a string.
+//
+//    RegisterCustomType(time.Time{}, Property{
+//      Type: "string",
+//      Format: "date-time",
+//    })
+//
+// Pointers to registered types will resolve to the same Property value unless
+// that pointer type has also been registered as a custom type.
+//
+// For example: registering time.Time will also apply to *time.Time, unless
+// *time.Time has also been registered.
+func RegisterCustomType(v interface{}, p Property) {
+	t := reflect.TypeOf(v)
+	p.GoType = t
+	customTypes[t] = p
+}
+
 func inspect(t reflect.Type, jsonTag string) Property {
+	if p, ok := customTypes[t]; ok {
+		return p
+	}
+
+	if t.Kind() == reflect.Ptr {
+		if p, ok := customTypes[t.Elem()]; ok {
+			return p
+		}
+	}
+
 	p := Property{
 		GoType: t,
 	}
@@ -174,6 +217,9 @@ func define(v interface{}) map[string]Object {
 		dirty = false
 		for _, d := range objMap {
 			for _, p := range d.Properties {
+				if _, ok := customTypes[p.GoType]; ok {
+					continue
+				}
 				if p.GoType.Kind() == reflect.Struct {
 					name := makeName(p.GoType)
 					if _, exists := objMap[name]; !exists {
diff --git a/swagger/reflect_test.go b/swagger/reflect_test.go
index 125dd66..bd9f43d 100644
--- a/swagger/reflect_test.go
+++ b/swagger/reflect_test.go
@@ -3,11 +3,12 @@ package swagger
 import (
 	"bytes"
 	"encoding/json"
+	"fmt"
 	"io/ioutil"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/assert"
-	"fmt"
 )
 
 type Person struct {
@@ -23,6 +24,8 @@ type Pet struct {
 	IntArray    []int
 	String      string
 	StringArray []string
+	Time        time.Time
+	TimePtr     *time.Time
 }
 
 type Empty struct {
@@ -40,7 +43,7 @@ func TestDefine(t *testing.T) {
 	obj, ok := v["swaggerPet"]
 	assert.True(t, ok)
 	assert.False(t, obj.IsArray)
-	assert.Equal(t, 8, len(obj.Properties))
+	assert.Equal(t, 10, len(obj.Properties))
 
 	content := map[string]Object{}
 	data, err := ioutil.ReadFile("testdata/pet.json")
@@ -114,3 +117,14 @@ func TestHonorJsonIgnore(t *testing.T) {
 	assert.False(t, obj.IsArray)
 	assert.Equal(t, 0, len(obj.Properties), "expected zero exposed properties")
 }
+
+func TestCustomTypes(t *testing.T) {
+	type ContainsCustomType struct {
+		TestTime time.Time `json:"testTime"`
+	}
+
+	obj := defineObject(ContainsCustomType{})
+
+	assert.Contains(t, obj.Properties, "testTime")
+	assert.EqualValues(t, "string", obj.Properties["testTime"].Type)
+}
diff --git a/swagger/testdata/pet.json b/swagger/testdata/pet.json
index c272e74..0ec8348 100644
--- a/swagger/testdata/pet.json
+++ b/swagger/testdata/pet.json
@@ -33,6 +33,14 @@
           "type": "string"
         }
       },
+      "Time": {
+        "type": "string",
+        "format": "date-time"
+      },
+      "TimePtr": {
+        "type": "string",
+        "format": "date-time"
+      },
       "friend": {
         "$ref": "#/definitions/swaggerPerson"
       },
@@ -53,4 +61,4 @@
       }
     }
   }
-}
\ No newline at end of file
+}