I have a company A with 12-period fiscal calendar in GL, which has fiscal year end in August. I have a related company B with 12-period fiscal calendar in GL, which has year end in March. Now I want to consolidate both A and B into company C, which has the same fiscal calendar in FX as, for instance, company A in GL. If I retrieve data from both A and B into C, fiscal periods will be translated one in one, and March (FP12) data from B will become to be August (FP12) data in C. What will be the best way to correct this?

In other words:
Is there any possibility to consolidate GL data from the companies having different fiscal calendars? Can fiscal period offset be configured before data retrieval? Alternatively, can departmental reporting be set in such manner so selected data in the report will depend not only on the period number, but also on the department? For consolidated departments, is there any way to have data selected based on the calendar dates, rather than on the period number?

Sorry, but FX is not designed to combine data sets with different fiscal calenders and have period-to-period comparisons work automatically. You'll have to design specialized statements.