diff --git a/scripts-available/CDB_DateToNumber.sql b/scripts-available/CDB_DateToNumber.sql
index 1b9a449..651d429 100644
--- a/scripts-available/CDB_DateToNumber.sql
+++ b/scripts-available/CDB_DateToNumber.sql
@@ -13,3 +13,19 @@ RETURN output;
 END;
 $$
 LANGUAGE 'plpgsql' STABLE STRICT;
+
+-- Convert timestamp with time zone to double precision
+--
+CREATE OR REPLACE FUNCTION CDB_DateToNumber(input timestamp with time zone)
+RETURNS double precision AS $$
+DECLARE output double precision;
+BEGIN
+    BEGIN
+        SELECT extract (EPOCH FROM input) INTO output;
+    EXCEPTION WHEN OTHERS THEN
+        RETURN NULL;
+    END;
+RETURN output;
+END;
+$$
+LANGUAGE 'plpgsql' STABLE STRICT;
diff --git a/test/CDB_DateToNumberTest.sql b/test/CDB_DateToNumberTest.sql
new file mode 100644
index 0000000..0c1051c
--- /dev/null
+++ b/test/CDB_DateToNumberTest.sql
@@ -0,0 +1,2 @@
+SELECT * FROM CDB_DateToNumber('1999-01-08 00:00:00'::timestamp);
+SELECT * FROM CDB_DateToNumber('1999-01-08 00:00:00+05'::timestamp with time zone);
diff --git a/test/CDB_DateToNumberTest_expect b/test/CDB_DateToNumberTest_expect
new file mode 100644
index 0000000..bd3d3b0
--- /dev/null
+++ b/test/CDB_DateToNumberTest_expect
@@ -0,0 +1,2 @@
+915753600
+915735600