=num(date(today(1)))*86400000 - num(date('1/1/1970'))*86400000
This will give you epoch time in milliseconds for a specified date. Qlik is storing dates as the number of days passed from 1/1/1900, whereas epoch time starts from 1970. Converting the date to milliseconds, and subtracting 1970, will give you the correct epoch time.
From https://community.qlik.com/t5/QlikView-App-Dev/Calculate-epoch-time-milliseconds/m-p/1251009/highlig...
