Pulsar positioning system: https://arxiv.org/pdf/1704.03316.pdf https://arxiv.org/pdf/1704.03316.pdf While not a primary source, it's still an answer to absolu

Pulsar positioning system: https://arxiv.org/pdf/1704.03316.pdf https://arxiv.org/pdf/1704.03316.pdf While not a primary source, it's still an answer to absolute time from pulsars: https://physics.stackexchange.com/questions/175981/can-you-use-pulsar-observations-to-determine-absolute-time-how-long-can-you-go https://physics.stackexchange.com/questions/175981/can-you-u...