DAYS360 third parameter should be Logical

6.10.7 DAYS360

Syntax: DAYS360( DateParam StartDate ; DateParam EndDate [ ; Integer Method = 0 ] )
Constraints: 0 <= Method <= 1
Semantics: If method is 0, it uses the National Association of
Securities Dealers (NASD) method, also known as the U.S.
method. If the method is 1, the European method is used.

LibreOffice Calc and Microsoft Excel and Gnumeric evaluate the Method
parameter as Logical (i.e. all values != 0 evaluate to TRUE). This
function should be specified as

Syntax: DAYS360( DateParam StartDate ; DateParam EndDate [ ; Logical Method = FALSE() ] )

Semantics: If method is FALSE(), it uses the National Association of
Securities Dealers (NASD) method, also known as the U.S.
method. If the method is TRUE(), the European method is used.

and the contraints be removed.

From Eike Rathke - https://lists.oasis-open.org/archives/office-comment/201605/msg00002.html