diff --git a/scripts-available/CDB_DateToNumber.sql b/scripts-available/CDB_DateToNumber.sql
index 84c3395..651d429 100644
--- a/scripts-available/CDB_DateToNumber.sql
+++ b/scripts-available/CDB_DateToNumber.sql
@@ -1,5 +1,21 @@
 -- Convert timestamp to double precision
 --
+CREATE OR REPLACE FUNCTION CDB_DateToNumber(input timestamp)
+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;
+
+-- 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;
diff --git a/test/CDB_DateToNumberTest.sql b/test/CDB_DateToNumberTest.sql
new file mode 100644
index 0000000..3821bd1
--- /dev/null
+++ b/test/CDB_DateToNumberTest.sql
@@ -0,0 +1,2 @@
+SELECT * FROM CDB_DateToNumber('1999-01-08 00:00:00+00'::timestamp);
+SELECT * FROM CDB_DateToNumber('1999-01-08 00:00:00+00'::timestamp with time zone);
diff --git a/test/CDB_DateToNumberTest_expect b/test/CDB_DateToNumberTest_expect
new file mode 100644
index 0000000..8445360
--- /dev/null
+++ b/test/CDB_DateToNumberTest_expect
@@ -0,0 +1,2 @@
+915753600
+915753600