Before this commit, the number of hours the task is open is computed using the resource calendar. The same measure expressed in days simply divide the number of hour by 24. This is not what we intend: we want to know the number of working days since the task was created, and not a simple conversion from hours to days. Task-37561 closes odoo/odoo#30092 Signed-off-by: Jérome Maes (jem) <jem@openerp.com>