There are 2 locations for this setting;
Setting this up from the Options menu will mean any future project will be created with these details by default:
Open ConQuest, Options, Number Options
Specify the number of minutes in an hour, hours in a day and days in a week.
Press OK, restart and reopen
The Project module tab allows you to set the details differently for specific Projects:
Open ConQuest, Projects, highlight specific project
Select the Min/Hours/Days option on top menu.
Specify the number of minutes in an hour, hours in a day and days in a week.
Press OK.