Kolkata, other Bengal cities to experience Zero Shadow Days; check dates, timings, and locations
KOLKATA: Residents of Kolkata and several other cities across Bengal will have a rare opportunity to witness a unique astronomical event twice in 2025 — the
Zero Shadow Day
(ZSD) — when vertical objects will cast no shadow at all for a brief moment around noon.
In Kolkata, this phenomenon will occur on June 5 at 11:34:54am and again on July 7 at 11:41:24 am (IST).
Zero Shadow Day occurs twice a year for locations situated between the Tropic of Cancer (23.5° N) and the Tropic of Capricorn (23.5° S) — the tropical zone of the Earth.
On these days, the Sun is exactly overhead at noon, causing vertical objects, including humans, to cast no visible shadow for a few moments. This happens because the Sun's declination (its apparent latitude in the sky) aligns perfectly with the geographic latitude of the location, said Bipas Das Gupta, Scientific Officer, M.
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P. Birla Institute of Fundamental Research.
At that moment, the Sun is at the zenith, the highest point in the sky directly above an observer. Due to the Sun's angular diameter of about half a degree, this phenomenon is observable for around 1 to 1.5 minutes, though viewers are advised to be ready at least 30 minutes before and after the scheduled time.
Apart from its visual appeal and educational value, Zero Shadow Day provides a hands-on opportunity to explore key astronomical concepts such as Earth's rotation, seasonal changes, solar declination, and the geometry of sunlight.
The event also mirrors how the ancient Greek scholar Eratosthenes famously estimated the Earth's circumference using shadow lengths in different cities.
Zero Shadow Days provide a fascinating link to Earth's position and motion in space. The Sun's apparent movement — northward during Uttarayan (January to June) and southward during Dakshinayan (July to December) — causes the Sun to be overhead at different places throughout the year.
ZSD occurs when the Sun's declination equals a location's latitude, which is why people in the tropics experience this twice annually, while those outside this zone never do.
The Tropic of Cancer — at latitude 23° 26' N — passes through Krishnanagar in West Bengal, one of only eight Indian states where this happens. Others include Gujarat, Rajasthan, Madhya Pradesh, Chhattisgarh, Jharkhand, Tripura, and Mizoram.
Zero Shadow Days Across West Bengal in 2025:
The dates and timings for key Bengal cities (all times in IST):
Kolkata: June 5, 11:34:54 am ; July 7, 11:41:24 am
Bardhaman: June 14, 11:38:44 am ; June 28, 11:41:45 am
Kharagpur: June 3, 11:38:52 am ; July 9, 11:45:58 am
Mayapur: June 19, 11:37:53 am ; June 23, 11:38:45 am
Diamond Harbour: June 2, 11:35:10 am ; July 10, 11:42:34 am
Krishnanagar: June 17, 11:36:58 am ; June 25, 11:38:43 am
Haldia: June 1, 11:35:29 am ; July 11, 11:43:10 am
Midnapur: June 4, 11:39:17 am ; July 8, 11:45:53 am
Barrackpur: June 7, 11:35:19 am ; July 5, 11:41:04 am
Baruipur: June 3, 11:34:24 am ; July 9, 11:41:30 am
Digha: May 29, 11:37:10 am ; July 14, 11:45:39 am
Purulia: June 16, 11:45:14 am ; June 27, 11:47:36 am
Kalyani: June 10, 11:35:38 am ; July 2, 11:40:16 am
Habra: June 8, 11:34:35 am ; July 4, 11:39:58 am
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