52 week period definition for forecasting

Hi

One of our client is working in E9.0 and using the forecasting (weekly). For our forecast generation, we use 52 week period (P0008B) as basis for extracting SO history (R3465) and generating forecast (R34650). Understand that oracle recommends not to setup this 52 weekly bucket between 2 different calendar years. My understanding is that weekly buckets 53 & 54 are not being used by forecast and planning programs. So when we define weekly periods across 2 different calendar years, the 53 and 54 bucket period demand will be messed up or not considered in our extract and forecast calculation. Is