They could've very easily had text on the screen saying what time period the current scene was in. It seems like they left it out deliberately for artistic reasons and many people have been confused as a result.
It does stray quite far from the books though. Especially the angle on infertility is hilarious. In books the infertility was a side effect of hormonal imbalance caused by the use of magic. Impossible to recover from for males, nearly impossible for females. With how they changed it in the series, I wonder how are they going to explain all those important characters, Geralt included, being sons of sorceresses.
They could have very easily made the series a collection of short stories too, but they trued to tie them tigether in an incoherent way instead. Very poor attempt, in my opinion, and I often enjoy cheap TV shows.
