Dating method
Stratigraphy
The order of layers and cuts. It says what came before what. It does not, alone, say which century.
What is observed
Soil, floors, walls, and pits stack and cut one another. If one layer seals another, the sealed layer was already there. A wall built over a floor is later than that floor. A pit dug through both is later still.
Published “layers” (for example an earlier round-building layer and a later rectangular-building layer) are a reading of that stack. They are useful, and they can be redrawn when more of a mound is excavated.
What it cannot do alone
Stratigraphy gives a sequence, not a count of years. To put the sequence on a calendar, excavators tie it to radiocarbon or to objects whose own dates are argued from typology. If those ties move, the calendar moves and the sequence of layers can stay.