Somewhere between version 7.0 and 7.6, TIBCO changed how the month function. It used to return an integer. Now it returns "Jan", "Feb", "Mar", etc. However, it is still an integer, even though the result returned looks like a string. This may cause issues if you are writing IF statements and referencing a column of expression using the month function. See screen shots below.
The month column is a calculated column using the expression month([Date]).
This if statement doesn't work because the column is an integer as indicated by the data type.
This if statement will work because it is using an integer rather than a string.