changed the start/end date fields to datetime fields, in order to allow more flexibility for the user and enable them to set a precise point in time at which ticket sales should start/end, because otherwise ticket sales/end would always be set at midnight which is not very flexible. Task-2431440 closes odoo/odoo#65133 Related: odoo/upgrade#2126 Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>