Date fields are usually recognized automatically by Tableau. For the dataset discussed here, the answer is YES.
However, problem appears when the date columns are pivoted. They are recognized as string data type.
And when they are just simply converted into date data type, it turned out to be wrong date as day is taken as month and month as day. It results that the target is only available for month of January (1st -12th of January) instead of from January to December.
This is when adjustment should be done manually using DATAPARSE() function.
How does it work? It basically force Tableau to parse or convert whatever format of date we have. It is telling Tableau that ‘hey I have date data type with format of dd/MM/yyyy, please recognize them as date and not as string’. However, because we tell Tableau manually, we have to adjust the format according to the Tableau Documentation. It can be found here Convert a Field to a Date Field.
In summary, there are 3 steps in order in case our dates aren’t interpreted correctly:
1. Change the data type of the field
2. Create a calculation using the DATEPARSE function
3. Create a calculation using the DATE function
Cheers,
Nuki