In addition to the accepted answer there are a tonne of pre-built custom functions available at https://github.com/beberlei/DoctrineExtensions .
These can be then registered in your config like
doctrine:
orm:
dql:
string_functions:
DATE: DoctrineExtensions\Query\Mysql\Date
and can then be used in your DQL (as in your query) like
DATE(jobs.endDate) AS endDate