Boulder Colorado: Sunrise/Sunset data and length of twilight
Go to Length of Twilight Table Add 1 hour to sunrise/sunset times for daylight savings time. Typically, it starts in March and ends in November.Lengths of day computed from sunset/sunrise times and are subject to rounding errors.
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
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
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 *daylight savings time starts 1997
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
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
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
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
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
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
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
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