How can Project Management be used without implementing any other financial modules?

We have a business requirement were we need to use Project Management module with Product Development, without using Finance module.
To achieve this, we have enabled project management without costing. However, while trying to Capture Progress of the project after setting a baseline, e are getting the error "You can't capture progress for this date because a planning period isn't defined. Create a planning period for the date, and capture progress. (PJO-2205214)" . Also, regarding the planning period, we have created a separate calendar for Projects, whose all periods are open, but not for Accounting Calendar, as we cannot open this. However, "copy from calendar" is disabled in the manage accounting periods screen, ence cannot proceed ahead.