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Ancient Astronomy and the British Shift: Till the advent of the colonial rule, India's time was governed by meticulous astronomical calculations rooted in the 4th-century CE treatise- the Surya Siddhanta.

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Ujjain as Zero Longitude: The treatise assumed a spherical Earth with the prime meridian passing through Avanti-which is modern Ujjain. Each major locality defined its own time by local almanacs known as Panchang, with references to the motions of celestial bodies.

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Railways Push for a National Standard: The expansion of the Indian Railways that began in 1853 required, for reasons both of operational efficiency and safety, a common time standard across the subcontinent.

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Madras Time as Precursor: The railways initially adopted the Madras Time-backe

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