Legal Metrology (Indian Standard Time) Rules 2026 Notified: IST Made Mandatory Across Official and Commercial Systems

Key facts

• The Department of Consumer Affairs notified the Legal Metrology (Indian Standard Time) Rules, 2026 on August 27, 2026.
• The rules establish Indian Standard Time (IST) as the common time reference for legal, administrative, commercial and other official purposes across India.
• The rules will come into force 180 days after their publication in the Official Gazette.
• IST is defined as the official time scale maintained by CSIR-National Physical Laboratory (CSIR-NPL), derived by adding five hours and 30 minutes to UTC(NPLI).
• CSIR-NPL generates UTC(NPLI) using caesium atomic clocks and hydrogen masers, with IST having a systematic uncertainty of about ±2.8 nanoseconds with respect to UTC.
• The government is developing infrastructure for disseminating accurate IST through Indian institutions and Legal Metrology laboratories, including provisions for using NavIC and other approved domestic timing sources.
• Under the 'One Nation, One Time' initiative, a White Rabbit Technology-based IST Dissemination Demonstration Network was commissioned at the Regional Reference Standard Laboratory in Bengaluru in July 2026.
• The Department of Consumer Affairs demonstrated secure dissemination of IST between the Bengaluru laboratory and NSE Chennai in collaboration with CSIR-NPL, ISRO, SEBI, NSE, BSNL and other stakeholders.