I believe there may be a bug in the server version of Qliksense.
If you create an app that uses the derived functions to create a calendar, something like this:
Calendar: DECLARE FIELD DEFINITION TAGGED '$date' Parameters first_month_of_year = 1 Fields Year($1) As Year Tagged '$year', Month($1) as Month Tagged '$month', Date($1) as Date Tagged ('$date', '$day'), Week($1) as Week Tagged '$week', Weekday($1) as Weekday Tagged '$weekday', DayNumberOfYear($1, first_month_of_year) as DayNumberOfYear Tagged ('$numeric');
Derive Fields From Fields Start Using Calendar;
Then reload it in your server app, it all works fine and you have a list of Date and time fields:
Then, use the QMC to manually reload the app:
If I then reload from the app editor, the fields return. Please note the reload does not fail whether done from the QMC or the Hub editor and in both cases all the other fields and data are fine.