diff --git a/backdrop/read/api.py b/backdrop/read/api.py
index fcae0a8a..dd15b50a 100644
--- a/backdrop/read/api.py
+++ b/backdrop/read/api.py
@@ -12,6 +12,7 @@
 from ..core.data_set import DataSet
 from ..core.database import InvalidOperationError
 from ..core.repository import DataSetConfigRepository
+from ..core.timeutils import as_utc
 
 
 GOVUK_ENV = getenv("GOVUK_ENV", "development")
@@ -43,7 +44,7 @@ def default(self, obj):
         if isinstance(obj, ObjectId):
             return str(obj)
         if isinstance(obj, datetime.datetime):
-            return obj.isoformat()
+            return as_utc(obj).isoformat()
         return json.JSONEncoder.default(self, obj)
 app.json_encoder = JsonEncoder
 
diff --git a/tests/read/test_read_api_json_encoder.py b/tests/read/test_read_api_json_encoder.py
new file mode 100644
index 00000000..78d3a9cb
--- /dev/null
+++ b/tests/read/test_read_api_json_encoder.py
@@ -0,0 +1,28 @@
+import unittest
+import pytz
+
+from hamcrest import *
+from datetime import datetime
+from backdrop.read.api import JsonEncoder
+
+
+class TestReadAPIJSONEcoder(unittest.TestCase):
+
+    def test_with_utc_date(self):
+        obj = {'date': datetime(2014, 4, 29, 1, 0, 0, 0, pytz.utc)}
+        assert_that(
+            JsonEncoder().encode(obj),
+            is_('{"date": "2014-04-29T01:00:00+00:00"}'))
+
+    def test_with_est_date(self):
+        est = pytz.timezone('US/Eastern')
+        obj = {'date': datetime(2014, 4, 29, 1, 0, 0, 0, est)}
+        assert_that(
+            JsonEncoder().encode(obj),
+            is_('{"date": "2014-04-29T06:00:00+00:00"}'))
+
+    def test_with_no_tz_date(self):
+        obj = {'date': datetime(2014, 4, 29, 1, 0)}
+        assert_that(
+            JsonEncoder().encode(obj),
+            is_('{"date": "2014-04-29T01:00:00+00:00"}'))