उन्हाळी प्रमाणवेळ

विकिपीडिया, मुक्‍त ज्ञानकोशातून
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ह्या लेखाचा/विभागाचा इंग्रजी किंवा अमराठी भाषेतून मराठी भाषेत भाषांतर करावयाचे बाकी आहे. अनुवाद करण्यास आपलाही सहयोग हवा आहे. ऑनलाईन शब्दकोश आणि इतर सहाय्या करिता भाषांतर प्रकल्पास भेट द्या.

उन्हाळी प्रमाणवेळ (किंवा ग्रीष्म प्रमाणवेळ) (इंग्लिश: Daylight saving time, summer time) ही जगातील अनेक देशांमध्ये उन्हाळ्यामधील स्थानिक प्रमाणवेळ आहे. विशेषतः शीत कटिबंधांमधील भागात उन्हाळ्यातील जास्त काळ टिकणाऱ्या सूर्यप्रकाशाचा फायदा घेण्यासाठी दरवर्षी वसंत ऋतूमध्ये स्थानिक वेळ एक तास पुढे ढकलली जाते व उन्हाळा संपल्यानंतर साधारण शरद ऋतूमध्ये ही वेळ एक तास मागे केली जाते. जॉर्ज व्हरनॉन हडसन ह्या न्यू झीलंडच्या शास्त्रज्ञाने १८९५ साली उन्हाळी प्रमाणवेळेची संकल्पना मांडली.

युरोपउत्तर अमेरिकेतील बहुसंख्य देश उन्हाळी प्रमाणवेळ वापरतात.

Diagram of a clock showing a transition from 2:00 to 3:00.
मध्य युरोपात उन्हाळी प्रमाणवेळ सुरू झाल्यावर घड्याळे २:०० वरून ३:०० वर ढकलली जातात.
Diagram of a clock showing a transition from 3:00 to 2:00.
मध्य युरोपात उन्हाळी प्रमाणवेळ संपताना घड्याळे ३:०० वरून पुन्हा २:०० वर आणली जातात.

उन्हाळी प्रमाणवेळेच्या वापराबाबत तज्‍ज्ञांमध्ये दुमत आहे. उन्हाळ्यात घड्याळ पुढे केल्यामुळे ऊर्जेची बचत होते असा समर्थकांचा दावा आहे तर शेतकऱ्यांना ह्या पद्धतीचा त्रास होतो अशी विरोधकांची भूमिका आहे.



G.V. Hudson invented modern DST, proposing it first in 1895.

Diagram of a clock showing a transition from 2:00 to 3:00.
When DST starts in central Europe, clocks advance from 02:00 CET to 03:00 CEST.
Diagram of a clock showing a transition from 3:00 to 2:00.
When DST ends in central Europe, clocks retreat from 03:00 CEST to 02:00 CET. Other regions switch at different times.
Time graph. The horizontal axis shows dates in 2008. The vertical axis shows the UTC offsets of eastern Brazil and eastern U.S. The difference between the two starts at 3 hours, then goes to 2 hours on February 17 at 24:00 Brazil eastern time, then goes to 1 hour on March 9 at 02:00 U.S. eastern time.
In early 2008 central Brazil was one, two, or three hours ahead of eastern U.S., depending on the date.

Benefits and drawbacks[संपादन]

A standing man in three-piece suit, facing camera. He is about 60 and is bald with a mustache. His left hand is in his pants pocket, and his right hand is in front of his chest, holding his pocket watch.
William Willett independently proposed DST in 1907 and advocated it tirelessly.[१]
Graph of sunrise and sunset times for 2007. The horizontal axis is the date; the vertical axis is the times of sunset and sunrise. There is a bulge in the center during summer, when sunrise is early and sunset late. There are step functions in spring and fall, when DST starts and stops.
Clock shifts affecting apparent sunrise and sunset times at Greenwich in 2007.[२]
A standing stone in a grassy field surrounded by trees. The stone contains a vertical sundial centered on 1 o'clock, and is inscribed "HORAS NON NUMERO NISI ÆSTIVAS" and "SUMMER TIME ACT 1925".
The William Willett Memorial Sundial is always on DST.
Poster titled "VICTORY! CONGRESS PASSES DAYLIGHT SAVING BILL" showing Uncle Sam turning a clock to daylight saving time as a clock-headed figure throws his hat in the air. The clock face of the figure reads "ONE HOUR OF EXTRA DAYLIGHT". The bottom caption says "Get Your Hoe Ready!"
Retailers generally favor DST. United Cigar Stores hailed a 1918 DST bill.
Strong man in sandals and with shaggy hair, facing away from artist, grabbing a hand of a clock bigger than he is and forcing it backwards. The clock uses Roman numerals and the man is dressed in stripped-down Roman gladiator style. The text says "You can't stop time... But you can turn it back one hour at 2 a.m. on Oct. 28 when daylight-saving time ends and standard time begins."
A 2001 U.S. public service advertisement reminded people to adjust clocks manually.

बाह्य दुवे[संपादन]

संदर्भ आणि नोंदी[संपादन]