Indian Standard Time keeping
Topic: Latitude, Longitude and Time · NCERT: Beyond NCERT
Meaning
Indian Standard Time (IST) is the one clock time used across India. It is the local time of the 82°30′E meridian, which passes near Mirzapur in Uttar Pradesh. Each degree of longitude equals 4 minutes, so 82.5 × 4 = 330 minutes, and IST = UTC + 5 h 30 min. The country's official time is generated and kept by CSIR-National Physical Laboratory (NPL), New Delhi, using atomic clocks, which are extremely accurate clocks. The draft Legal Metrology (IST) Rules 2024 would make IST compulsory for official, legal and commercial use (verify current).
Example
CSIR-NPL in New Delhi runs the atomic clocks that set India's official time. Railways, banks, telecom networks and satellite navigation all need time that is exact to a tiny fraction of a second. This makes accurate timekeeping strategic infrastructure, meaning a system the country depends on.
Don't confuse with
- Local time: this is a place's own sun-based time, set by the sun over its meridian. IST is a single standard time for the whole country, so in Assam local time is not the same as IST.
- UTC (Coordinated Universal Time): this is the world reference time, kept by atomic clocks worldwide and coordinated by BIPM. IST is India's national time, set 5:30 hours ahead of UTC.