GR - POSTING PERIOD

Respected gurus,

While posting the GR for PO i am receiving one error about my posting period.

" Posting only possible in periods 2007/08 and 2008/ 07 for company code xxx " error message M7053

What could be the reason of the same.

Can you tell me exactly the significance of the posting period and also how to check my current posting period for the company code.

If any change is required in the same how to carry out the same.

Please guide me.