nextday function not working with edate and eomonth functions

[GoingIncognito]

I was reading through SQLBI instruction that had a line:  NEXTDAY ( SAMEPERIODLASTYEAR ( LASTDATE ( Calendar[FullDate] ) ) )

So being unimaginitive, as I am, I tried NEXTDAY ( EDATE( LASTDATE(fact[date]), -13 ) ) ) and  NEXTDAY ( EOMONTH( LASTDATE(fact[date]), -13 ) ) ). By taking out nextday I get a result, but with Nextday() I get a "A function 'LASTDATE' has been used in a True/False expression that is used as a table filter expression. This is not allowed." Why do I get this? Why isn't nextday() allowed? 

[az38]

hi @GoingIncognito 

maybe that will be enough?

Column = Edate(lastdate(fact[date]),-13)+1

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[GoingIncognito]

That's what I did. But didn't come with a better place to ask, why doesn't nextday() work here? I would like to know, out of curiosity. Thank you for your reply!

[az38 · Accepted solution]

@GoingIncognito 

EDATE https://docs.microsoft.com/en-us/dax/edate-function-dax or EOMONTH https://docs.microsoft.com/en-us/dax/eomonth-function-dax returns the DATE. well. like a string in text format

but for NEXTDAY https://docs.microsoft.com/en-us/dax/nextday-function-dax input is A column containing dates. 

It is not so clear but there is a difference

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