Data display in P Book

I have Monthly Bkts in My Pl Book. When my history is loaded into my PA, how the data for the dates 1- 5 Jan 08 is displayed ? Will it show under Dec 07 bkt or Jan 08 bkt in pl book ? as 31st Dec 07 is monday. So the whole week data will fall under Dec bkt ?

Any idea pls ?

thx

venkat