To add new date format to OS Services Booking, you can add the format into Configuration page and select it.
Please open file: administrator > components > com_osservicesbooking > classes > configuration.php
Code:
$format_date_times = explode('|','d.m.Y, H:i|d.m.Y, H:i:s|m.d.Y, H:i|m.d.Y, H:i:s|Y.m.d, H:i|Y.m.d, H:i:s|j.n.Y, H:i|j.n.Y, H:i:s|n.j.Y, H:i|n.j.Y, H:i:s|Y.n.j, H:i|Y.n.j, H:i:s|d/m/Y, H:i|d/m/Y, H:i:s|m/d/Y, H:i|m/d/Y, H:i:s|Y/m/d, H:i|Y/m/d, H:i:s|j/n/Y, H:i|j/n/Y, H:i:s|n/j/Y, H:i|n/j/Y, H:i:s|Y/n/j, H:i|Y/n/j, H:i:s|d-m-Y, H:i|d-m-Y, H:i:s|m-d-Y, H:i|m-d-Y, H:i:s|Y-m-d, H:i|Y-m-d, H:i:s|j-n-Y, H:i|j-n-Y, H:i:s|n-j-Y, H:i|n-j-Y, H:i:s|Y-n-j, H:i|Y-n-j, H:i:s');
