Ok people this is how you can travel through time. These are the requirements and ways of getting through each time zone: Requirement item: red gem (no jewel shard can time travel like the red gem can. the jewel shard in Inuyasha is specifically for and only for the well that leads from Feudal era to Modern Japan and vice versa.)

First as everyone knows the well that connects from Feudal to Modern Japan.
From Feudal to Shogun: a cave deep into the forest.
From Shogun to Meiji: the attic inside the house where Oda Nobunaga's family lives. Then
Meiji to Heian (which is beyond all the eras closest to Modern) you take a train to a hidden valley and basically fall into the raveen.