if Unix format is number of seconds since 1970/01/01, and QlikView format is number of days since 1900/01/01,it's rather simple to calculate:
QlikView date for 1970/01/01 is 25569. From here, add the number of days based on the Unix Date:
QV Date = 25569 + <UnixDate> / 24 hours / 60 minutes / 60 seconds
This formula might be off by a day, play with it before implementing.