Question on Home Sale Gains Exclusion for Widow

[Kim Bayless]

I keep getting conflicting answers when researching, so hoping someone current on the changes can help me out. My father passed away in February 2018. My mother was told she must sell their home by the end of 2018 to qualify for the married $500K gains exclusion. If it sells after that, she only gets the $250K single exclusion. Is this correct?? I see where it changed from one year to 2 years in 2007, but did it change back to 1 year now?