Boulder Colorado: Sunrise/Sunset data and length of twilight

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Add 1 hour to sunrise/sunset times for daylight savings time. Note Daylight savising starts Mar 10 and ends Nov 3.
Lengths of day computed from sunset/sunrise times and are subject to rounding errors.

Months

 

January

 

       Sunrise Sunset Length-of-Day

  1     7:21     4:46     9:25
  2     7:21     4:47     9:26
  3     7:21     4:48     9:27
  4     7:21     4:49     9:28
  5     7:21     4:50     9:29
  6     7:21     4:50     9:29
  7     7:21     4:51     9:30
  8     7:21     4:52     9:31
  9     7:21     4:52     9:31
 10     7:21     4:53     9:32
 11     7:21     4:55     9:34
 12     7:21     4:56     9:35
 13     7:20     4:57     9:37
 14     7:20     4:59     9:39
 15     7:20     5:00     9:40
 16     7:19     5:01     9:42
 17     7:19     5:02     9:43
 18     7:18     5:03     9:45
 19     7:18     5:04     9:46
 20     7:17     5:05     9:48
 21     7:17     5:06     9:49
 22     7:16     5:08     9:52
 23     7:15     5:09     9:54
 24     7:15     5:10     9:55
 25     7:14     5:11     9:57
 26     7:13     5:12     9:59
 27     7:13     5:13    10:00
 28     7:12     5:15    10:03
 29     7:11     5:16    10:05
 30     7:10     5:17    10:07
 31     7:09     5:18    10:09
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February

 

       Sunrise Sunset Length-of-Day
  1     7:08     5:19    10:11
  2     7:07     5:21    10:14
  3     7:07     5:22    10:15
  4     7:06     5:23    10:17
  5     7:05     5:24    10:19
  6     7:03     5:25    10:22
  7     7:02     5:27    10:25
  8     7:01     5:28    10:27
  9     7:00     5:29    10:29
 10     6:59     5:30    10:31
 11     6:58     5:31    10:33
 12     6:57     5:32    10:35
 13     6:56     5:34    10:38
 14     6:54     5:35    10:41
 15     6:53     5:36    10:43
 16     6:52     5:37    10:45
 17     6:50     5:38    10:48
 18     6:49     5:39    10:50
 19     6:48     5:41    10:53
 20     6:47     5:42    10:55
 21     6:45     5:43    10:58
 22     6:44     5:44    11:00
 23     6:42     5:45    11:03
 24     6:41     5:46    11:05
 25     6:40     5:47    11:07
 26     6:38     5:48    11:10
 27     6:37     5:50    11:13
 28     6:35     5:51    11:16
 29     6:35     5:52    11:17
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March

 

(Add 1 hour after daylight savings time starts)
       Sunrise Sunset Length-of-Day
  1     6:34     5:52    11:18
  2     6:32     5:53    11:21
  3     6:31     5:54    11:23
  4     6:29     5:55    11:26
  5     6:28     5:56    11:28
  6     6:26     5:57    11:31
  7     6:25     5:58    11:33
  8     6:23     5:59    11:36
  9     6:22     6:00    11:38
 10     6:20     6:01    11:41
 11     6:18     6:02    11:44
 12     6:17     6:03    11:46
 13     6:15     6:04    11:49
 14     6:14     6:06    11:52
 15     6:12     6:07    11:55
 16     6:11     6:08    11:57
 17     6:09     6:09    12:00
 18     6:07     6:10    12:03
 19     6:06     6:11    12:05
 20     6:04     6:12    12:08
 21     6:01     6:13    12:12
 22     6:01     6:14    12:13
 23     5:59     6:15    12:16
 24     5:58     6:16    12:18
 25     5:56     6:17    12:21
 26     5:54     6:18    12:24
 27     5:53     6:19    12:26
 28     5:51     6:20    12:29
 29     5:50     6:21    12:31
 30     5:48     6:22    12:34
 31     5:46     6:23    12:37
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April

 

(add 1 hour for daylight savings time, if in effect)
       Sunrise Sunset Length-of-Day
  1     5:45     6:24    12:39
  2     5:43     6:25    12:42
  3     5:42     6:26    12:44
  4     5:40     6:27    12:47
  5     5:38     6:28    12:50
  6     5:37     6:29    12:52 
  7     5:35     6:30    12:55 
  8     5:34     6:31    12:57
  9     5:32     6:32    13:00
 10     5:31     6:33    13:02
 11     5:29     6:34    13:05
 12     5:28     6:35    13:07
 13     5:26     6:36    13:10
 14     5:25     6:37    13:12
 15     5:23     6:38    13:15
 16     5:22     6:39    13:17
 17     5:20     6:40    13:20
 18     5:19     6:41    13:22
 19     5:17     6:42    13:25
 20     5:16     6:43    13:27
 21     5:14     6:44    13:30
 22     5:13     6:45    13:32
 23     5:12     6:46    13:34
 24     5:10     6:47    13:37
 25     5:09     6:48    13:39
 26     5:07     6:49    13:42
 27     5:06     6:50    13:44
 28     5:05     6:51    13:46
 29     5:04     6:52    13:48
 30     5:02     6:53    13:51
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May

 

(add 1 hour for daylight savings time, if in effect)
       Sunrise Sunset Length-of-Day
  1     5:01     6:54    13:53
  2     5:00     6:55    13:55
  3     4:59     6:56    13:57
  4     4:57     6:57    14:00
  5     4:56     6:58    14:02
  6     4:55     6:59    14:04
  7     4:54     7:00    14:06
  8     4:53     7:01    14:08
  9     4:52     7:02    14:10
 10     4:51     7:03    14:12
 11     4:50     7:04    14:14
 12     4:49     7:05    14:16
 13     4:48     7:06    14:18
 14     4:47     7:06    14:19
 15     4:46     7:07    14:21
 16     4:45     7:08    14:23
 17     4:44     7:09    14:25
 18     4:43     7:10    14:27
 19     4:42     7:11    14:29
 20     4:41     7:12    14:31
 21     4:41     7:13    14:32
 22     4:40     7:14    14:34
 23     4:39     7:15    14:36
 24     4:38     7:15    14:37
 25     4:38     7:16    14:38
 26     4:37     7:17    14:40
 27     4:37     7:18    14:41
 28     4:36     7:19    14:43
 29     4:35     7:19    14:44
 30     4:35     7:20    14:45
 31     4:34     7:21    14:47
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June

 

(add 1 hour for daylight savings time, if in effect)
       Sunrise Sunset Length-of-Day
  1     4:34     7:22    14:48
  2     4:34     7:22    14:48
  3     4:33     7:23    14:50
  4     4:33     7:24    14:51
  5     4:33     7:24    14:51
  6     4:32     7:25    14:53
  7     4:32     7:26    14:54
  8     4:32     7:26    14:54
  9     4:32     7:27    14:55
 10     4:32     7:27    14:55
 11     4:31     7:28    14:57
 12     4:31     7:28    14:57
 13     4:31     7:29    14:58
 14     4:31     7:29    14:58
 15     4:31     7:30    14:59
 16     4:31     7:30    14:59
 17     4:31     7:30    14:59
 18     4:31     7:31    15:00
 19     4:32     7:31    14:59
 20     4:32     7:31    14:59
 21     4:32     7:31    14:59
 22     4:32     7:32    15:00
 23     4:32     7:32    15:00
 24     4:33     7:32    14:59
 25     4:33     7:32    14:59
 26     4:33     7:32    14:59
 27     4:34     7:32    14:58
 28     4:34     7:32    14:58
 29     4:34     7:32    14:58
 30     4:35     7:32    14:57
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July

 

(add 1 hour for daylight savings time, if in effect)
       Sunrise Sunset Length-of-Day
  1     4:35     7:32    14:57
  2     4:36     7:32    14:56
  3     4:36     7:32    14:56
  4     4:37     7:31    14:54
  5     4:37     7:31    14:54
  6     4:38     7:31    14:53
  7     4:39     7:31    14:52
  8     4:39     7:30    14:51
  9     4:40     7:30    14:50
 10     4:41     7:30    14:49
 11     4:41     7:29    14:48
 12     4:42     7:29    14:47
 13     4:43     7:28    14:45
 14     4:43     7:28    14:45
 15     4:44     7:27    14:43
 16     4:45     7:27    14:42
 17     4:46     7:26    14:40
 18     4:46     7:25    14:39
 19     4:47     7:25    14:38
 20     4:48     7:24    14:36
 21     4:49     7:23    14:34
 22     4:50     7:23    14:33
 23     4:51     7:22    14:31
 24     4:51     7:21    14:30
 25     4:52     7:20    14:28
 26     4:53     7:19    14:26
 27     4:54     7:18    14:24
 28     4:55     7:17    14:22
 29     4:56     7:16    14:20
 30     4:57     7:15    14:18
 31     4:58     7:14    14:16
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August

 

(add 1 hour for daylight savings time, if in effect)
       Sunrise Sunset Length-of-Day
  1     4:58     7:13    14:15
  2     4:59     7:12    14:13
  3     5:00     7:11    14:11
  4     5:01     7:10    14:09
  5     5:02     7:09    14:07
  6     5:03     7:08    14:05
  7     5:04     7:07    14:03
  8     5:05     7:06    14:01
  9     5:06     7:04    13:58
 10     5:07     7:03    13:56
 11     5:08     7:02    13:54
 12     5:09     7:01    13:52
 13     5:10     6:59    13:49
 14     5:11     6:58    13:47
 15     5:12     6:57    13:45
 16     5:13     6:55    13:42
 17     5:13     6:54    13:41
 18     5:14     6:53    13:39
 19     5:15     6:51    13:36
 20     5:16     6:50    13:34
 21     5:17     6:48    13:31
 22     5:18     6:47    13:29
 23     5:19     6:45    13:26
 24     5:20     6:44    13:24
 25     5:21     6:42    13:21
 26     5:22     6:41    13:19
 27     5:23     6:39    13:16
 28     5:24     6:38    13:14
 29     5:25     6:36    13:11
 30     5:26     6:35    13:09
 31     5:27     6:33    13:06
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September

 

(add 1 hour for daylight savings time, if in effect)
       Sunrise Sunset Length-of-Day
  1     5:28     6:32    13:04
  2     5:28     6:30    13:02
  3     5:29     6:29    13:00
  4     5:30     6:27    12:57
  5     5:31     6:25    12:54
  6     5:32     6:24    12:52
  7     5:33     6:22    12:49
  8     5:34     6:21    12:47
  9     5:35     6:19    12:44
 10     5:36     6:17    12:41
 11     5:37     6:16    12:39
 12     5:38     6:14    12:36
 13     5:39     6:12    12:33
 14     5:40     6:11    12:31
 15     5:41     6:09    12:28
 16     5:42     6:08    12:26
 17     5:42     6:06    12:24
 18     5:43     6:04    12:21
 19     5:44     6:03    12:19
 20     5:45     6:01    12:16
 21     5:46     5:59    12:13
 22     5:47     5:58    12:11
 23     5:48     5:56    12:08
 24     5:49     5:54    12:05
 25     5:50     5:53    12:03
 26     5:51     5:51    12:00
 27     5:52     5:50    11:58
 28     5:53     5:48    11:55
 29     5:54     5:46    11:52
 30     5:55     5:45    11:50
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October

 

(add 1 hour for daylight savings time, if in effect)
       Sunrise Sunset Length-of-Day
  1     5:56     5:43    11:47
  2     5:57     5:41    11:44
  3     5:58     5:40    11:42
  4     5:59     5:38    11:39
  5     6:00     5:37    11:37
  6     6:01     5:35    11:34
  7     6:02     5:33    11:31
  8     6:03     5:32    11:29
  9     6:04     5:30    11:26
 10     6:05     5:29    11:24
 11     6:06     5:27    11:21
 12     6:07     5:26    11:19
 13     6:08     5:24    11:16
 14     6:09     5:23    11:14
 15     6:10     5:21    11:11
 16     6:11     5:20    11:09
 17     6:12     5:18    11:06
 18     6:13     5:17    11:04
 19     6:14     5:15    11:01
 20     6:15     5:14    10:59
 21     6:16     5:13    10:57
 22     6:17     5:11    10:54
 23     6:18     5:10    10:52
 24     6:19     5:09    10:50
 25     6:20     5:07    10:47
 26     6:22     5:06    10:44
 27     6:23     5:05    10:42
 28     6:24     5:03    10:39
 29     6:25     5:02    10:37
 30     6:26     5:01    10:35
 31     6:27     5:00    10:33
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November

 

(add 1 hour for daylight savings time, if in effect)
       Sunrise Sunset Length-of-Day
  1     6:28     4:58    10:30
  2     6:29     4:57    10:28
  3     6:31     4:56    10:25  
  4     6:32     4:55    10:23
  5     6:33     4:54    10:21
  6     6:34     4:53    10:19
  7     6:35     4:52    10:17
  8     6:36     4:51    10:15
  9     6:37     4:50    10:13
 10     6:39     4:49    10:10
 11     6:40     4:48    10:08
 12     6:41     4:47    10:06
 13     6:42     4:46    10:04
 14     6:43     4:45    10:02
 15     6:44     4:45    10:01
 16     6:45     4:44     9:59
 17     6:47     4:43     9:56
 18     6:48     4:42     9:54
 19     6:49     4:42     9:53
 20     6:50     4:41     9:51
 21     6:51     4:40     9:49
 22     6:52     4:40     9:48
 23     6:53     4:39     9:46
 24     6:54     4:39     9:45
 25     6:55     4:38     9:43
 26     6:56     4:38     9:42
 27     6:58     4:37     9:39
 28     6:59     4:37     9:38
 29     7:00     4:37     9:37
 30     7:01     4:36     9:35
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December

 

       Sunrise Sunset Length-of-Day
  1     7:02     4:36     9:34
  2     7:03     4:36     9:33
  3     7:04     4:36     9:32
  4     7:05     4:36     9:31
  5     7:06     4:35     9:29
  6     7:06     4:35     9:29
  7     7:07     4:35     9:28
  8     7:08     4:35     9:27
  9     7:09     4:35     9:26
 10     7:10     4:35     9:25
 11     7:11     4:36     9:25
 12     7:12     4:36     9:24
 13     7:12     4:36     9:24
 14     7:13     4:36     9:23
 15     7:14     4:36     9:22
 16     7:14     4:37     9:23
 17     7:15     4:37     9:22
 18     7:16     4:37     9:21
 19     7:16     4:38     9:22
 20     7:17     4:38     9:21
 21     7:17     4:39     9:22
 22     7:18     4:39     9:21
 23     7:18     4:40     9:22
 24     7:19     4:40     9:21
 25     7:19     4:41     9:22
 26     7:20     4:41     9:21
 27     7:20     4:42     9:22
 28     7:20     4:43     9:23
 29     7:21     4:44     9:23
 30     7:21     4:44     9:23
 31     7:21     4:45     9:24
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Duration of Civil Twilight at 40N`
		
Day Jan   Feb   Mar   Apr   May   Jun   Jul   Aug   Sep   Oct   Nov   Dec
  1  30    29    27    27    29    32    33    30    28    27    28    30
  9  30    28    27    28    30    33    32    30    27    27    29    30
 17  30    28    27    28    31    33    32    29    27    27    29    31 
 25  29    27    27    29    32    33    31    28    27    28    30    31

 

Data is for curiosity only; there are no guarantees that the data is correct. If you notice any obvious errors, I'll correct them.