Yes, you can use Date#() function for this. It takes two parameters: a string with date value and a string defining date format. So in your exmple:
Of course you can use field names as the first parameter:
Hope this helps
Date#() generates the same period, but makes Qlik understand it is a date field. So after using Date#() on your period field you can work with it as with date field. Try Chanty's example to see for yourself
Date(Date#(PeriodField, 'MM.YYYY'), 'DD.MM.YYYY')
You need to complete the date then change it,
DATE(DATE#('01.'&DateField,'DD.MM.YYYY'),'DD.MM.YYYY') AS NewDate
This will make all your period the 1st of the month.