Suppress a compiler warning under OpenVMS; time_t is unsigned on (at least) the more recent versions of that platform, so we use the value (time_t)(-1) as the error value. This is the type used in the OpenVMS documentation: http://www.openvms.compaq.com/commercial/c/5763p048.htm#inde This closes SF tracker bug #404240. Also clean up an exception message when detecting overflow of time_t values beyond 4 bytes.