Volume at CloseBaytex and 7 other energy companies are being added to sp/tsx index effective Mon Dec 20th. Any index fund that tracks sp/tsx would have to buy by the close today or even at open on Mon.
Here's the link to the changes to sp/tsx for Dec 20
https://money.tmx.com/en/quote/BTE/news/8895011425016353/SP_Dow_Jones_Indices_Announces_Changes_to_the_SPTSX_Composite_Index