Andy tells Prue that the lady from the bookstore was half covered in debris and her face was contorted. When they show her lying there, her face is normal and there isn't anything covering her body.
Tanjella claims that the evil energy convergence occurs every 1300 years on Friday the 13th. There is no recorded evidence of any superstitions regarding Friday the 13th before the 19th century and most reasons for claiming the day as unlucky go back to the last supper of Jesus. Since that time there has only been one full cycle of 1300 years so it would be impossible for such a pattern to exist.
Until October 1582 Christian society lived by the Julian calendar. Pope Gregory XIII modified the year by a quarter day, the Gregorian calendar. This adjusted the drift between the real solar year and the calendar year. Thursday 4 October 1582 was followed by Friday 15 October 1582. So the Gregorian Friday the 13th has noting to do with the one 1300 years before. For more information search Wikipedia.
When the girls are eating lunch at Quake, Prue accidentally knocks over the salt and pepper shakers and Piper goes on a rant about spilled salt and how it's bad luck. However the close up of the shakers falling over clearly shows pepper spilling out, not salt.
When Tanjela is killed in the prologue, her hair turns pale white. But it's obvious that she's wearing a wig because of her side burn where she still reveals her natural red hair when we see a closeup of her face.
At the end of Phoebe's interview, when the realtor's lover shows up, Phoebe says "Taking a romantic mid-week break?" It has already been established that the day is Friday thus, not mid-week.