diff --git a/sdf/1.5/schema/types.xsd b/sdf/1.5/schema/types.xsd
index 53f3d8db6..3d1215ace 100644
--- a/sdf/1.5/schema/types.xsd
+++ b/sdf/1.5/schema/types.xsd
@@ -31,7 +31,9 @@
   </xsd:simpleType>
 
   <xsd:simpleType name="time">
-    <xsd:restriction base="xsd:double">
+    <xsd:restriction base="xsd:string">
+      <xsd:whiteSpace value="collapse"/>
+      <xsd:pattern value="\d+ \d+"/>
     </xsd:restriction>
   </xsd:simpleType>
 
diff --git a/sdf/1.6/schema/types.xsd b/sdf/1.6/schema/types.xsd
index 53f3d8db6..3d1215ace 100644
--- a/sdf/1.6/schema/types.xsd
+++ b/sdf/1.6/schema/types.xsd
@@ -31,7 +31,9 @@
   </xsd:simpleType>
 
   <xsd:simpleType name="time">
-    <xsd:restriction base="xsd:double">
+    <xsd:restriction base="xsd:string">
+      <xsd:whiteSpace value="collapse"/>
+      <xsd:pattern value="\d+ \d+"/>
     </xsd:restriction>
   </xsd:simpleType>
 
diff --git a/sdf/1.7/schema/types.xsd b/sdf/1.7/schema/types.xsd
index 53f3d8db6..3d1215ace 100644
--- a/sdf/1.7/schema/types.xsd
+++ b/sdf/1.7/schema/types.xsd
@@ -31,7 +31,9 @@
   </xsd:simpleType>
 
   <xsd:simpleType name="time">
-    <xsd:restriction base="xsd:double">
+    <xsd:restriction base="xsd:string">
+      <xsd:whiteSpace value="collapse"/>
+      <xsd:pattern value="\d+ \d+"/>
     </xsd:restriction>
   </xsd:simpleType>
 
diff --git a/sdf/1.8/schema/types.xsd b/sdf/1.8/schema/types.xsd
index 53f3d8db6..3d1215ace 100644
--- a/sdf/1.8/schema/types.xsd
+++ b/sdf/1.8/schema/types.xsd
@@ -31,7 +31,9 @@
   </xsd:simpleType>
 
   <xsd:simpleType name="time">
-    <xsd:restriction base="xsd:double">
+    <xsd:restriction base="xsd:string">
+      <xsd:whiteSpace value="collapse"/>
+      <xsd:pattern value="\d+ \d+"/>
     </xsd:restriction>
   </xsd:simpleType>