Normally Qlik Sense does a great job of picking up whether the field is a date or text. Sometimes you get some data thats fallen off the back of a lorry that doesn’t seem to be identified correctly by Qlik Sense automatically.
You can use the table viewer to see what Qlik has tagged fields as if you are unsure why date and time or string functions are not working the way you expect.
A typical thing is to check whether a date is actually being stored correctly as a date. You can check this quickly by selecting the field name in the table viewer and examining the $tags that have been assigned to the field. You would expect to see $date or $timestamp on a date field, or $text on a text field.
Making the most of the table viewers subtle hints can save you lots of time and banging head against the wall.