diff --git a/pkg/api/unversioned/duration.go b/pkg/api/unversioned/duration.go
new file mode 100644
index 00000000000..d9209f2c3e1
--- /dev/null
+++ b/pkg/api/unversioned/duration.go
@@ -0,0 +1,47 @@
+/*
+Copyright 2014 The Kubernetes Authors All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package unversioned
+
+import (
+	"encoding/json"
+	"time"
+)
+
+// Duration is a wrapper around time.Duration which supports correct
+// marshaling to YAML and JSON. In particular, it marshals into strings, which
+// can be used as map keys in json.
+type Duration struct {
+	time.Duration
+}
+
+// UnmarshalJSON implements the json.Unmarshaller interface.
+func (d *Duration) UnmarshalJSON(b []byte) error {
+	var str string
+	json.Unmarshal(b, &str)
+
+	pd, err := time.ParseDuration(str)
+	if err != nil {
+		return err
+	}
+	d.Duration = pd
+	return nil
+}
+
+// MarshalJSON implements the json.Marshaler interface.
+func (d Duration) MarshalJSON() ([]byte, error) {
+	return json.Marshal(d.String())
+}
diff --git a/pkg/api/unversioned/duration_test.go b/pkg/api/unversioned/duration_test.go
new file mode 100644
index 00000000000..6650ca9aa16
--- /dev/null
+++ b/pkg/api/unversioned/duration_test.go
@@ -0,0 +1,153 @@
+/*
+Copyright 2014 The Kubernetes Authors All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package unversioned
+
+import (
+	"encoding/json"
+	"testing"
+	"time"
+
+	"github.com/ghodss/yaml"
+)
+
+type DurationHolder struct {
+	D Duration `json:"d"`
+}
+
+func TestDurationMarshalYAML(t *testing.T) {
+	cases := []struct {
+		input  Duration
+		result string
+	}{
+		{Duration{5 * time.Second}, "d: 5s\n"},
+		{Duration{2 * time.Minute}, "d: 2m0s\n"},
+		{Duration{time.Hour + 3*time.Millisecond}, "d: 1h0m0.003s\n"},
+	}
+
+	for _, c := range cases {
+		input := DurationHolder{c.input}
+		result, err := yaml.Marshal(&input)
+		if err != nil {
+			t.Errorf("Failed to marshal input: %q: %v", input, err)
+		}
+		if string(result) != c.result {
+			t.Errorf("Failed to marshal input: %q: expected %q, got %q", input, c.result, string(result))
+		}
+	}
+}
+
+func TestDurationUnmarshalYAML(t *testing.T) {
+	cases := []struct {
+		input  string
+		result Duration
+	}{
+		{"d: 0s\n", Duration{}},
+		{"d: 5s\n", Duration{5 * time.Second}},
+		{"d: 2m0s\n", Duration{2 * time.Minute}},
+		{"d: 1h0m0.003s\n", Duration{time.Hour + 3*time.Millisecond}},
+
+		// Units with zero values can optionally be dropped
+		{"d: 2m\n", Duration{2 * time.Minute}},
+		{"d: 1h0.003s\n", Duration{time.Hour + 3*time.Millisecond}},
+	}
+
+	for _, c := range cases {
+		var result DurationHolder
+		if err := yaml.Unmarshal([]byte(c.input), &result); err != nil {
+			t.Errorf("Failed to unmarshal input %q: %v", c.input, err)
+		}
+		if result.D != c.result {
+			t.Errorf("Failed to unmarshal input %q: expected %q, got %q", c.input, c.result, result)
+		}
+	}
+}
+
+func TestDurationMarshalJSON(t *testing.T) {
+	cases := []struct {
+		input  Duration
+		result string
+	}{
+		{Duration{5 * time.Second}, `{"d":"5s"}`},
+		{Duration{2 * time.Minute}, `{"d":"2m0s"}`},
+		{Duration{time.Hour + 3*time.Millisecond}, `{"d":"1h0m0.003s"}`},
+	}
+
+	for _, c := range cases {
+		input := DurationHolder{c.input}
+		result, err := json.Marshal(&input)
+		if err != nil {
+			t.Errorf("Failed to marshal input: %q: %v", input, err)
+		}
+		if string(result) != c.result {
+			t.Errorf("Failed to marshal input: %q: expected %q, got %q", input, c.result, string(result))
+		}
+	}
+}
+
+func TestDurationUnmarshalJSON(t *testing.T) {
+	cases := []struct {
+		input  string
+		result Duration
+	}{
+		{`{"d":"0s"}`, Duration{}},
+		{`{"d":"5s"}`, Duration{5 * time.Second}},
+		{`{"d":"2m0s"}`, Duration{2 * time.Minute}},
+		{`{"d":"1h0m0.003s"}`, Duration{time.Hour + 3*time.Millisecond}},
+
+		// Units with zero values can optionally be dropped
+		{`{"d":"2m"}`, Duration{2 * time.Minute}},
+		{`{"d":"1h0.003s"}`, Duration{time.Hour + 3*time.Millisecond}},
+	}
+
+	for _, c := range cases {
+		var result DurationHolder
+		if err := json.Unmarshal([]byte(c.input), &result); err != nil {
+			t.Errorf("Failed to unmarshal input %q: %v", c.input, err)
+		}
+		if result.D != c.result {
+			t.Errorf("Failed to unmarshal input %q: expected %q, got %q", c.input, c.result, result)
+		}
+	}
+}
+
+func TestDurationMarshalJSONUnmarshalYAML(t *testing.T) {
+	cases := []struct {
+		input Duration
+	}{
+		{Duration{}},
+		{Duration{5 * time.Second}},
+		{Duration{2 * time.Minute}},
+		{Duration{time.Hour + 3*time.Millisecond}},
+	}
+
+	for i, c := range cases {
+		input := DurationHolder{c.input}
+		jsonMarshalled, err := json.Marshal(&input)
+		if err != nil {
+			t.Errorf("%d-1: Failed to marshal input: '%v': %v", i, input, err)
+		}
+
+		var result DurationHolder
+		if err := yaml.Unmarshal(jsonMarshalled, &result); err != nil {
+			t.Errorf("%d-2: Failed to unmarshal '%+v': %v", i, string(jsonMarshalled), err)
+		}
+
+		if input.D != result.D {
+			t.Errorf("%d-4: Failed to marshal input '%#v': got %#v", i, input, result)
+		}
+	}
+}