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Measurement, standards and time
India now has a legal time. The Legal Metrology (Indian Standard Time) Rules, 2026 require government and critical sector systems to run on a traceable, authorised source of Indian Standard Time, in place of whatever each was taking from satellite or telecom signals. The time itself is generated by atomic clocks at the CSIR-National Physical Laboratory (CSIR-NPL), and the rules take effect 180 days after publication.
UPSC has asked
- Prelims 2018: uses of GPS technology, including banking and power grids
How traceable IST reaches a user
Atomic clocks
CSIR-NPL's clock ensemble and primary frequency standard generate UTC(NPLI).
Link to UTC
UTC(NPLI) is kept within a few nanoseconds of Coordinated Universal Time.
IST
Indian Standard Time is UTC(NPLI) plus 5 hours 30 minutes.
Regional copies
Secondary time scales at five Regional Reference Standard Laboratories, plus NavIC and National Informatics Centre (NIC) services.
Users
Banks, telecom, power grids and government systems synchronise and show traceability.
Who does what
- CSIR-NPL, India's National Metrology Institute, generates the national time scale with its atomic clocks and supplies traceability to it.
- The Legal Metrology Department regulates and enforces, as it already does for shop weights and petrol pump gauges.
- NavIC, the satellite navigation system the Indian Space Research Organisation (ISRO) built after the Global Positioning System (GPS) was denied to India during the Kargil War, takes its own time reference from CSIR-NPL.
Why time needed a legal standard
- Many systems took time indirectly from GPS or from a telecom provider, sources that can differ by seconds or even minutes.
- Guidelines of 2023 from the Indian Computer Emergency Response Team (CERT-In) already asked government systems to synchronise with NPL and NIC, because tracing a cyber incident needs trustworthy time stamps.
What has happened
1 Sep 2026
The Legal Metrology (Indian Standard Time) Rules, 2026, made under the Legal Metrology Act, 2009, gave time legal status for the first time.
- Time dependent systems in government and in critical sectors must take Indian Standard Time from a traceable, authorised source and be able to show that traceability.
- The rules take effect 180 days after publication, and serve the stated vision of One Nation, One Time.
PIB, 2 Sep 2026: Legal Metrology (Indian Standard Time) Rules, 2026 Notified: Major Step Towards "One Nation, One Time" (opens in a new tab) · The Indian Express, 1 Sep 2026: Why India is making IST legally enforceable: An expert explains (opens in a new tab)