Dilation is freedom, until people you care about run at a different speed. Staying together means the faster one slows down — and gives up subjective years they'll never live. This measures that cost (§28).
◆ In-world canon · §28Every resident sets their own clock. Run fast and a single calendar year becomes decades of subjective life — but the people you love may run at other speeds, and time spent together has to happen at the slower of your two rates. So closeness carries a price, paid by whoever gives up the most subjective time to match the other. This tool puts a number on it.
Subjective years = rate × calendar years. At 50× for 200 calendar years you live 10,000 subjective years — the canon figure, and enough for "hundreds of direct descendants" (estimated here as one new direct descendant per ~25 subjective years of family life; each conception also dedicates a fresh Layer-0 server, so the 20-offspring Layer-1 cap is a hard limit per person).
The sacrifice is the gap: if a friend at 200× drops to your 50× to stay in sync, they forgo (200 − 50) = 150 subjective years per calendar year — over 10 years, 1,500 subjective years of unlived experience. That is the moral arithmetic §28 puts in front of every close relationship across a dilation gap. The synchronous Universal Sabbath is the only time the gap closes for free.
Pairs with the Time Dilation Instrument (your own clock) — this one is about the distance a clock opens up between two people.
Further reading: Sahlstein, E. (2004). "Relating at a distance: Negotiating being together and being apart in long-distance relationships." Journal of Social and Personal Relationships, 21(5), 689–710 — on the asymmetric costs of maintaining close relationships across temporal/geographic gaps. Einstein, A. (1905). "Zur Elektrodynamik bewegter Körper." Annalen der Physik, 17 — original special relativity, from which the physics of subjective time dilation follows.