Legal Metrology (Indian Standard Time) Rules, 2026 notified for 'One Nation, One Time'
On 27 August 2026, the Department of Consumer Affairs notified the Legal Metrology (Indian Standard Time) Rules, 2026, making IST the common legal time reference; the Rules take effect 180 days after Gazette publication.
Summary
The Department of Consumer Affairs notified the Legal Metrology (Indian Standard Time) Rules, 2026 on 27 August 2026, and the Rules were published in the Official Gazette on 29 August 2026. The Rules make Indian Standard Time (IST) the common time reference for legal, administrative, commercial and official purposes, and come into force 180 days after Gazette publication. CSIR-National Physical Laboratory (CSIR-NPL), India's National Metrology Institute, generates IST with an ensemble of atomic clocks and keeps it traceable within a few nanoseconds to Coordinated Universal Time (UTC), maintained by the International Bureau of Weights and Measures (BIPM). The Rules allow NavIC and other approved Indian timing sources for dissemination, and secondary timescales have been set up at five Regional Reference Standard Laboratories at Ahmedabad, Bengaluru, Bhubaneswar, Faridabad and Guwahati. The initiative supports the 'One Nation, One Time' vision and builds on a White Rabbit IST dissemination network commissioned at RRSL Bengaluru in July 2026.
Key facts
- Rules
- Legal Metrology (Indian Standard Time) Rules, 2026
- Notified / Gazette
- 27 August 2026 / 29 August 2026
- In force
- 180 days after Gazette publication
- Notified by
- Department of Consumer Affairs
- IST custodian
- CSIR-NPL (National Metrology Institute); traceable to UTC (BIPM)
- Timing sources
- NavIC and other approved Indian sources
- RRSLs
- Ahmedabad, Bengaluru, Bhubaneswar, Faridabad, Guwahati
Practice MCQs 4 questions
The Legal Metrology (Indian Standard Time) Rules, 2026 were notified by which department?
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Correct answer: D — Department of Consumer Affairs
The Department of Consumer Affairs notified the Rules on 27 August 2026.
When will the Legal Metrology (Indian Standard Time) Rules, 2026 come into force?
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Correct answer: D — 180 days after publication in the Official Gazette
The Rules come into force 180 days from their publication in the Official Gazette (29 August 2026), giving organisations time to adapt systems.
Consider the following statements about Indian Standard Time (IST) under the 2026 framework: 1. CSIR-NPL generates IST using an ensemble of atomic clocks and keeps it traceable to UTC. 2. UTC is maintained by the International Bureau of Weights and Measures (BIPM). Which of the above is/are correct?
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Correct answer: C — Both 1 and 2
Both are correct: CSIR-NPL, India's National Metrology Institute, generates IST with atomic clocks traceable within nanoseconds to UTC, which BIPM maintains.
Secondary IST timescales have been set up at Regional Reference Standard Laboratories (RRSLs) in five cities. Which of the following is NOT one of them?
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Correct answer: B — Kolkata
The five RRSLs are at Ahmedabad, Bengaluru, Bhubaneswar, Faridabad and Guwahati; Kolkata is not among them.