The Indian government has introduced new regulations to formalise Indian Standard Time as the sole legal time reference nationwide, enhancing consistency across government and infrastructure sectors while addressing cybersecurity and resilience concerns.
India has moved closer to making Indian Standard Time the single legal reference for civil, commercial and official use nationwide, after the Ministry of Consumer Affairs, Food and Public Distribution notified the Legal Metrology (Indian Standard Time) Rules, 2026 on 27 August. The measure is designed to reduce fragmentation in how time is recorded and displayed across government, business and infrastructure systems, and will take effect 180 days after publication in the Official Gazette.
The rules give IST a formal role in legal, administrative and commercial activity, meaning references to time in official documents will generally need to follow the national standard unless another reference is specifically permitted. IST is maintained by the CSIR-National Physical Laboratory and is defined as UTC(NPLI) plus 5 hours and 30 minutes. The framework was first set out in draft form in January 2025, when the Department of Consumer Affairs invited public comment on a broader plan to standardise timekeeping across sectors.
The new regime also narrows the use of other time references. Foreign time zones may still be shown where another law, order or guideline allows it, but they must be clearly labelled alongside IST. Alternative time scales can be used for scientific research, navigation and astronomy, although only with prior approval. In practice, this means other time standards are not banned outright, but their use will be tightly controlled.
Public-facing institutions will be required to synchronise time-dependent systems with an authorised source traceable to UTC(NPLI). The rules specifically mention railway stations, airports and government offices, which will have to display IST using an accurate and traceable timing source. Critical sectors such as telecommunications, financial services, energy and data centres face stricter obligations, including the need for redundant synchronisation systems and back-up timing arrangements so that failures do not disrupt operations.
The government has also placed emphasis on resilience and cybersecurity. The rules refer to threats such as jamming, spoofing and cyber attacks, and require contingency planning as well as secure hardware, software and procedures. Authorised timing sources include NPLI, Regional Reference Standards Laboratories, the National Informatics Centre and NavIC-based devices, with dissemination through systems such as Network Time Protocol and Precision Time Protocol. NavIC, ISRO’s regional navigation satellite system, is expected to play a central role in providing timing references for critical infrastructure, while atomic clocks calibrated by NPLI or regional laboratories may be used as highly stable back-up sources. The Legal Metrology Division will oversee compliance through periodic audits.
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