Just got off the phone with a CSR.
SPG Fiscal year ends at the end on February. I asked her straight-up if its better to get my match after that date and she said yes. @Chaikel, your match came after, and being that they always give at least 1 year, they extended you to the next fiscal end (2013). @Dan, yours was before that date(your post was mid-Feb). That being the case, all matches and challenges should be done in month of March, and they will give you the Plat status for approx 23 months.
As for the Challenge, I just started mine today. It will be dated 01/01 and run through the end of March. If I end up short a few stays, I will start a new challenge and use my previous two months and end it end of April.