India, Aug. 31 -- A failed UPI payment between two banks can be reconciled only if both banks' servers agree on when it was attempted. An investigator trying to reconstruct the order of trades in a market-manipulation case needs to know, to the microsecond, which order was placed first. A grid operator working out why a substation tripped depends on time-stamped fault records. For each of these tasks, there needs to be a mechanism that we all take for granted today: that every clock involved in the world is telling the same time, to the millisecond or better.

Today, that mechanism is mostly an approximation. India's banks, exchanges, telecom networks, power grids and data centres draw time from a mix of sources - the CSIR-National Physic...