Max(date) not resulting in number format

[Shriya]

Generally, we have seen that when we write Max(date) in chart then it results in  number  format ex: 156725, but in my case it is directly resulting in date format.

Also when I uses expressions which contains such variables then in general it uses num for comparison of dates

Ex: {<[Invoice Date]={">=$(=num(vStartDate))<=$()=num(vEndDate)"}>}

but here it is not showing data and if we removes 'num', then the data gets appeared,

where vEndDate=date(max([Invoice Date]),'DD-MM-YY').

Please help me to solve this issue.

[Vegar]

You are changing the Invoice Date from a date to a num to a date to a num again.

What about using this simplified version instead 

 {<[Invoice Date]={">=$(=min([Invoice Date]))<=$(=max([Invoice Date]))"}>}