LM IST Rules 2026

REGD. No. D. L.-33004/99 The Gazette of India CG-DL-E-29082026-275852 EXTRAORDINARY PART II—Section 3—Sub-section (i) PUBLISHED BY AUTHORITY No. 695] NEW DELHI, THURSDAY, AUGUST 27, 2026/BHADRA 5, 1948 MINISTRY OF CONSUMER AFFAIRS, FOOD AND PUBLIC DISTRIBUTION (Department of Consumer Affairs) NOTIFICATION New Delhi, the 27th August, 2026 G.S.R. 761(E). — In exercise of the powers conferred by section 52 of the Legal Metrology Act, 2009, (1 of 2010), the Central Government hereby makes the following rules, namely:- (1) Short title and commencement.- (1) These rules may be called as the Legal Metrology (Indian Standard Time) Rules, 2026. (2) They shall come into force after one hundred and eighty days from the date of publication in the Official Gazette. 2. Definitions.- In these rules, unless the context otherwise requires,- (a) "accuracy" means the degree to which a time or frequency value conforms to the official reference time either Coordinated Universal Time (National Physical Laboratory India) [UTC (NPLI)] or Indian Standard Time (IST); (b) "Act" means the Legal Metrology Act, 2009 (1 of 2010); (c) "Authorised Timing Source" means any institution, system or service authorised by the Director (Legal Metrology), subject to such technical, operational, security, traceability and compliance requirements as may be specified from time to time, for the dissemination of UTC(NPLI) or Indian Standard Time and whose authorisation may be suspended or revoked by the Director (Legal Metrology) for non-compliance with these Rules or the conditions of authorisation, after giving a reasonable opportunity of being heard. (d) "Coordinated Universal Time (UTC)" means the international reference time scale computed and published by the International Bureau of Weights and Measures (BIPM) based on data contributed by participating national timing laboratories; (e) "end entity" means any person, user, organisation or system receiving and using time obtained from an authorised timing source; (f) "Indian Standard Time (IST)" means the official time scale for all civil, commercial and legal purposes in India, realised and maintained by the Council of Scientific and Industrial Research - National Physical Laboratory and derived by adding an offset of 5 hours and 30 minutes to UTC(NPLI); (g) "NavIC" means Navigation with Indian Constellation, developed by Indian Space Research Organisation; (h) "RRSL" means Regional Reference Standards Laboratories established by the Government; (i) "timing reference” means a source of traceable and accurate time used to synchronise systems, networks or infrastructure; (j) “UTC(NPLI)" means the realisation of Coordinated Universal Time (UTC) at Council of Scientific and Industrial Research -National Physical Laboratory; (k) Words and expressions used herein and not defined but defined in the Act, shall have the meanings respectively assigned to them in the Act. 3. Purpose and scope.— These rules shall provide the framework for the generation, maintenance, dissemination, synchronisation, traceability and use of Indian Standard Time (IST) in accordance with the provisions of the Legal Metrology Act, 2009, with a view to ensuring uniform adoption and synchronisation of Indian Standard Time (IST) across the country and promoting accuracy, reliability, traceability, operational efficiency, resilience and security in governance, public services, commerce, industry, critical infrastructure and by the public at large. 4. Base unit of time.- The base unit of time shall be the second (symbol-'s'), defined by taking the fixed numerical value of the caesium frequency AVcs, the unperturbed ground-state hyperfine transition frequency of caesium-133 atom, to be 9192631770 when expressed in the unit Hz, equal to s¯¹. 5. Format of Indian Standard Time (IST).- (1) The standard format of Indian Standard Time (IST) is HH:MM:SS (2) The standard format for Indian Standard Time (IST) with date is DD-MM-YYYY- HH:MM:SS (3) The Council of Scientific and Industrial Research - National Physical Laboratory shall maintain the primary time scale of India, UTC (NPLI) and realise Indian Standard Time (IST), with traceability to the UTC. (4) The Council of Scientific and Industrial Research - National Physical Laboratory, Regional Reference Standards Laboratories, Indian Space Research Organisation and other authorised timing sources shall disseminate UTC (NPLI) and Indian Standard Time (IST) through its official time and frequency services. (5) The Legal Metrology Division shall be responsible for the establishment, maintenance and traceability of all secondary time scales at RRSLs to ensure traceability to the IST. 6. Reference to time.- (1) All references to time in legal, administrative and official documents shall be Indian Standard Time (IST) unless explicitly stated otherwise. (2) The Indian Standard Time (IST) shall be the standard time reference across all sectors, including commerce, transport, public administration, legal contracts and financial operations. (3) The authorised timing source shall maintain accuracy and traceability of its time synchronisation to UTC (NPLI) or Indian Standard Time (IST). (4) An authorised timing source shall provide a time signal traceable to the UTC (NPLI) or Indian Standard Time (IST) and the end entity shall bear the exclusive responsibility for ensuring the accuracy, stability and traceability of the time dependent within its systems. (5) The Council of Scientific and Industrial Research-National Physical Laboratory and other authorised timing sources may maintain a public webpage displaying the official Indian Standard Time (IST) and while such source shall provide a time signal traceable to the national time standard, the end user shall be responsible for monitoring deviations recording them in accordance with international standards and maintains auditable data to demonstrate traceability of its time to the national time standard. 7. Prohibition of other time references.- No entity shall use, display or record any time reference other than Indian Standard Time (IST) for all purposes: Provided that if any law in force or orders or directions or guidelines permits for display of time of foreign time zones with clear labelling alongside Indian Standard Time (IST), alternate time scales may be used for scientific research, navigation or astronomy with prior approval. 8. Public display and use of Indian Standard Time (IST).- (1) The Government offices and public institutions shall synchronise time-dependent applications and public time displays to Indian Standard Time (IST) through an authorised timing source specified in these rules. (2) The specific addresses or access protocols for designated NTP, PTP or any other authorised means or NavIC services including domain names or public internet protocol addresses, shall be published and maintained by the Director (Legal Metrology). (3) Major public locations, including railways, airports and Government offices, shall display Indian Standard Time (IST) synchronised with a traceable source as defined in these rules with accuracy. (4) Entities operating within critical sectors, including telecommunications, financial services, energy and data centers, shall ensure that time-dependent systems are synchronised to Indian Standard Time (IST) using an authorised time source traceable to UTC (NPLI), namely,- (i) NPLI; or (ii) RRSL; or (iii) NavIC based timing reference/device; or (iv) National Informatics Centre; or (v) other authorised timing sources. (5) The authorised timing sources shall provide time dissemination services using standard protocols, including Network Time Protocol (NTP) and Precision Time Protocol (PTP) and the Director, Legal Metrology may specify subscription fee for such services. 9. Cybersecurity and resiliency.- (1) The time-synchronisation systems shall incorporate robust cybersecurity measures to safeguard against malicious attacks. (2) The end-entity shall employ a redundant time synchronisation system to ensure continuous time traceable to UTC (NPLI) or Indian Standard Time (IST). (3) All entities and organisations shall implement and maintain a comprehensive contingency plan to mitigate potential disruptions, including jamming, spoofing and cyber-attacks, affecting their time-synchronisation systems. (4) The information technology security guidelines for time-synchronisation systems aimed at protecting the integrity, confidentiality and availability of service of Time-synchronisation systems as specified by the Central Government or such authority as may be authorised by it. (5) The time-synchronisation systems shall,- (i) utilise a secure housing, hardware, software and procedures to protect against unauthorised intrusion and misuse; (ii) provide a dependable level of reliability in their services, suited for the performance of their intended function; (iii) adhere to security procedures to ensure that accountability, availability, reliability and traceability of time are maintained; and (iv) comply with such standards, guidelines and procedures as may be specified by the Government: Provided that such standards do not compromise the security and integrity of the system. (6) To safeguard national and economic security, all critical infrastructure sectors including defence, power grids, utilities, telecommunications, banking and finance, transportation, enterprises, broadcasting, data centers, etc. shall utilise a redundant time synchronization system and such system shall incorporate the NavIC or one or more authorised timing sources as a timing reference in addition to other authorised timing source. (7) To build resiliency, all global navigation satellite systems based timing devices shall receive at least one timing reference directly from the NavIC constellation or from an authorised timing source. (8) All entities and organisations shall integrate one or more authorised timing sources into their timing infrastructure to mitigate disruptions and ensure continuity of network operations and mission-critical services. (9) The user shall implement mechanisms to maintain uninterrupted timing services in the event of reference input failures by employing highly stable and precise atomic clocks calibrated by Council of Scientific and Industrial Research - National Physical Laboratory or Regional Reference Standard Laboratories or by sourcing time from authorised timing sources. 10. Compliance and monitoring.- (1) The periodic audits shall be conducted to ensure compliance with these rules. (2) All Regional Reference Standard Laboratories and other authorised timing sources shall be subject to such audits to verify the traceability and availability of Indian Standard Time (IST). (3) The Council of Scientific and Industrial Research - National Physical Laboratory, shall maintain UTC (NPLI) and ensure its traceability to Coordinated Universal Time (UTC). (4) The Legal Metrology Division shall oversee and enforce compliance with these rules. 11. Penalties.- (1) where any person or agency has breached the provisions of these rules, directions or orders made thereunder, shall be punishable under the provisions of the Act. (2) The Director, Legal Metrology or an authorised officer, shall conduct an inquiry and impose penalty in case of breach of the provisions under this Act. [F. No. I-9/1/2025-W&M] ANUPAM MISHRA, Addl. Secy.