Max(date) , GROUP BY INVALID EXPRESSION

[HamidFOUNAS]

Hello ,
please, I want to load the maximum of date_reelle   group by service demande_service but I have a message erreur , 

invalid expression 

thank you for helping me

LOAD demande_service,
max(date(date_reelle)) as datep;

[affectation_traitement_3]:
SELECT
date_reelle,
`demande_service`
FROM app.`affectation_traitement`
GROUP BY demande_service;

[BrunPierre]

[affectation_traitement_3]:

LOAD demande_service,
max(date(date_reelle)) as datep

GROUP BY demande_service;

SELECT
date_reelle,
`demande_service`
FROM app.`affectation_traitement`;