Observations logged from the twilight meridian. Each reading taken at the boundary between certainty and drift, where two standards of measurement overlap and neither yields to the other.
The line where two reckonings diverge. East of here, time is counted forward. West, it is counted again. The double standard persists at every crossing.
The fixed point is an illusion. Every anchor drags. Every standard, given enough current, reveals itself as arbitrary. What holds is not the ground but the tension in the chain.
A single beam, two frequencies. The keeper logs the hours but the light answers to a different clock. What you see depends on where you stand and which standard you trust.