In date.lisp, clsql-date/times->utime, passes timezone to encode-universal-time, and the comment says you can pass nil, and the test clsql-date/times->utime-test tests this.
But timezone is defined to be a rational number (http://www.lispworks.com/documentation/lw71/CLHS/Body/26_glo_t.htm#time_zone), so this is illegal call.
Can fix it by passing (or timezone 0) instead.