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  1. #!ruby
  2. # -*- encoding: UTF-8 -*-
  3.  
  4. =begin
  5. お題
  6.  
  7. https://e...content-available-to-author-only...h.edu/docs/transit_algorithms.html
  8.  
  9. まずこのｻｲﾄを読んで日時(UTC基準)からJDを求めるﾌﾟﾛｸﾞﾗﾑを作りなさい
  10. 逆にJDから日時(UTC基準)を求めるﾌﾟﾛｸﾞﾗﾑも作りなさい 
  11.  
  12. このｻｲﾄに書いてあるとおりに作るとﾌﾟﾛｸﾞﾗﾑの結果は正しくならない
  13.  
  14. ﾌﾟﾛｸﾞﾗﾑの結果が正しくなるように修正し、
  15. このｻｲﾄのどこに誤記があるかその箇所を指摘しなさい 
  16.  
  17. #####################################################################
  18.  
  19. 	日付への変換式が間違っている
  20. -	e = int[365.25/d]
  21. +	e = int[365.25*d] # または int[365.25d]
  22.  
  23. # frac は整数限定で % 1 にした
  24.  
  25. =end
  26.  
  27.  
  28. # JD = int[365.25y] + int[30.6001(m+1)]+B+1720996.5+D+UT/24.
  29. def jd( dy, dm, dd, th, tm, ts )
  30. 	if dm <= 2
  31. 		dy -= 1
  32. 		dm += 12
  33. 	end
  34. 	if dy < 1582 || dy == 1582 && ( dm < 10 || dm == 10 && dd < 15 )
  35. 		b = -2
  36. 	else
  37. 		b = dy.div(400) - dy.div(100)
  38. 	end
  39. 	ut = th + tm.fdiv(60) + ts.fdiv(3600)
  40.  
  41. 	(365.25*dy).to_i + (30.6001*(dm+1)).to_i + b + 1720996.5 + dd + ut.fdiv(24)
  42. end
  43.  
  44. def dmy( jd )
  45. 	a = (jd+0.5).to_i
  46. 	if a >= 2299161
  47. 		b = ( (a-1867216.25).fdiv(36524.25) ).to_i
  48. 		c = a + b - b.div(4) + 1525
  49. 	else
  50. 		c = a + 1524
  51. 	end
  52. 	d = ( (c-122.1)/365.25 ).to_i
  53. 	e = ( 365.25*d ).to_i		### e 	= int[365.25/d] --> int[365.25d]
  54. 	f = ( (c-e)/30.6001 ).to_i
  55.  
  56. 	dd = c - e - (30.6001*f).to_i + (jd + 0.5) % 1		# frac jd > 0
  57. 	dm = f - 1 - 12*f.div(14)
  58. 	dy = d - 4715 - (7 + dm).div(10)
  59.  
  60. 	[dy,dm,dd]
  61. end
  62.  
  63. 	utm = Time.now.utc
  64. 	puts utm.strftime( '      %Y/%m/%d %T (%Z)' )
  65. 	jd = jd( utm.year, utm.mon, utm.day, utm.hour, utm.min, utm.sec )
  66. 	puts "JD  = #{jd}"
  67. 	dy,dm,dd = dmy( jd )
  68. 	puts "YMD = %d/%02d/%02d (UTC)" % [dy,dm,dd]
  69.  
  70.  
Success #stdin #stdout 0s 28224KB
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      2018/10/08 17:38:41 (UTC)
JD  = 2458400.2351967595
YMD = 2018/10/08 (UTC)
https://ideone.com/SKS4yj
Julian Day
language:
Ruby (ruby 2.5.5)
created:
5 years ago
visibility:
public

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