Index: ammosreader/PDW.py
===================================================================
--- ammosreader/PDW.py	(revision 9dc7beb5dc05ab14365716e3cc5e8966cb593b47)
+++ ammosreader/PDW.py	(revision 7a9c06895cb39f25674d09d7d877461f20bc0cef)
@@ -24,8 +24,11 @@
         :rtype: PDW
         """
-        assert(len(byte_string) == 32)
+        if (len(byte_string) != 32):
+            raise TypeError("Too many bytes")
 
         parts = struct.unpack('<Q4s4s4s4s4s4s', byte_string)
         nanoseconds = (parts[0])
+        if (np.datetime64('now', 'ns').astype(int) >= nanoseconds):
+            raise OverflowError("Timestamp invalid")
         time_of_arrival = np.datetime64(nanoseconds, 'ns')