It first started (1981) as qualifying and heats on Saturday and B mains and features on Sunday afternoon. Then went to qualifying and heats on Friday....B mains and features on Saturday. I remember one year (maybe 92 or 93) when they qualified on Thursday, heats on Friday and the B mains and features on Saturday. I also remember when the fastest 6 qualifiers were locked into the feature and didn't have to run a heat race.