spss trend module

[Restu-2]

Hi all,
  I'm new to the list. I have a question to those who are familiar with spss trend module, especially how it works in calculating seasonality/forecasting.

  I work for a retail business that always measures things on a weekly basis. The problem though is that in year 2006 there are 53 weeks total instead of 52 normally.

  Because of that, the week is shifted in 2007. So week 1 of 2007 is comparable to week 2 of 2006, week 24 of 2007 is comparable to week 25 of 2006 and so on.

  Now, when forecasting with SPSS trend, I am afraid the software can't calculate or identify seasonality because of the week shift. Therefore, my question is, should i remove one of the weeks in 2006? If i were to remove, do i need to remove the week 1 or week 53?

  Please advice.

  Thanks in advance,
  restu