By definition the Equation of Time = apparent solar time minus mean solar time.
The day number of the year (DOY) can be obtained by adding the day of the month to the values given below:
0 January 31 February 59 March 90 April 120 May 151 June 181 July 212 August 243 September 273 October 304 November 334 DecemberThus, March 10th is the 59 + 10 = 69th day of the year. September 12th is the 243 + 12 = 255th day of the year. This is valid for non-leap years such as 2007. In leap years you have to add 1 day starting March 1st. Thus, in 2008, June 3rd is the 151 + 3 + 1 = 155th day of that leap year.
Given below are values of the Equation of Time, in decimal minutes, for each day of the year. The values were generated using the approximate formula provided by Jean Meeus. Apparently, his algorithm can be in error up to 30 seconds from the true value. That would be 1/8 of a degree of longitude or 7.5'.
Day of Year ET
(minutes of time)
1 -3.6069
2 -4.0536
3 -4.4956
4 -4.9324
5 -5.3637
6 -5.7890
7 -6.2079
8 -6.6202
9 -7.0253
10 -7.4229
11 -7.8127
12 -8.1943
13 -8.5674
14 -8.9316
15 -9.2867
16 -9.6324
17 -9.9682
18 -10.2940
19 -10.6095
20 -10.9144
21 -11.2084
22 -11.4914
23 -11.7631
24 -12.0232
25 -12.2717
26 -12.5082
27 -12.7326
28 -12.9448
29 -13.1447
30 -13.3320
31 -13.5066
32 -13.6686
33 -13.8177
34 -13.9539
35 -14.0771
36 -14.1873
37 -14.2845
38 -14.3686
39 -14.4396
40 -14.4976
41 -14.5426
42 -14.5745
43 -14.5935
44 -14.5996
45 -14.5930
46 -14.5736
47 -14.5416
48 -14.4972
49 -14.4404
50 -14.3715
51 -14.2905
52 -14.1977
53 -14.0933
54 -13.9773
55 -13.8501
56 -13.7119
57 -13.5630
58 -13.4034
59 -13.2336
60 -13.0538
61 -12.8642
62 -12.6652
63 -12.4570
64 -12.2400
65 -12.0144
66 -11.7807
67 -11.5390
68 -11.2899
69 -11.0335
70 -10.7703
71 -10.5006
72 -10.2248
73 -9.9433
74 -9.6563
75 -9.3644
76 -9.0679
77 -8.7672
78 -8.4627
79 -8.1547
80 -7.8437
81 -7.5300
82 -7.2141
83 -6.8963
84 -6.5771
85 -6.2569
86 -5.9360
87 -5.6149
88 -5.2939
89 -4.9734
90 -4.6538
91 -4.3356
92 -4.0191
93 -3.7046
94 -3.3926
95 -3.0833
96 -2.7773
97 -2.4748
98 -2.1762
99 -1.8819
100 -1.5921
101 -1.3072
102 -1.0276
103 -0.7535
104 -0.4852
105 -0.2231
106 0.0326
107 0.2816
108 0.5235
109 0.7583
110 0.9855
111 1.2051
112 1.4167
113 1.6201
114 1.8152
115 2.0017
116 2.1794
117 2.3483
118 2.5082
119 2.6588
120 2.8001
121 2.9320
122 3.0543
123 3.1671
124 3.2701
125 3.3633
126 3.4468
127 3.5204
128 3.5841
129 3.6380
130 3.6820
131 3.7161
132 3.7404
133 3.7549
134 3.7597
135 3.7549
136 3.7405
137 3.7166
138 3.6834
139 3.6409
140 3.5894
141 3.5289
142 3.4596
143 3.3817
144 3.2953
145 3.2007
146 3.0981
147 2.9876
148 2.8696
149 2.7442
150 2.6117
151 2.4723
152 2.3264
153 2.1741
154 2.0158
155 1.8518
156 1.6824
157 1.5078
158 1.3284
159 1.1445
160 0.9564
161 0.7645
162 0.5691
163 0.3705
164 0.1692
165 -0.0347
166 -0.2406
167 -0.4482
168 -0.6573
169 -0.8674
170 -1.0781
171 -1.2891
172 -1.5000
173 -1.7105
174 -1.9201
175 -2.1286
176 -2.3356
177 -2.5406
178 -2.7433
179 -2.9435
180 -3.1406
181 -3.3344
182 -3.5245
183 -3.7106
184 -3.8923
185 -4.0692
186 -4.2412
187 -4.4078
188 -4.5687
189 -4.7236
190 -4.8722
191 -5.0142
192 -5.1494
193 -5.2774
194 -5.3980
195 -5.5108
196 -5.6158
197 -5.7126
198 -5.8010
199 -5.8807
200 -5.9517
201 -6.0136
202 -6.0662
203 -6.1095
204 -6.1432
205 -6.1672
206 -6.1814
207 -6.1856
208 -6.1796
209 -6.1635
210 -6.1372
211 -6.1004
212 -6.0532
213 -5.9956
214 -5.9275
215 -5.8488
216 -5.7597
217 -5.6599
218 -5.5497
219 -5.4290
220 -5.2979
221 -5.1564
222 -5.0047
223 -4.8427
224 -4.6706
225 -4.4885
226 -4.2966
227 -4.0949
228 -3.8836
229 -3.6630
230 -3.4331
231 -3.1942
232 -2.9465
233 -2.6901
234 -2.4253
235 -2.1524
236 -1.8716
237 -1.5832
238 -1.2874
239 -0.9845
240 -0.6748
241 -0.3586
242 -0.0363
243 0.2920
244 0.6257
245 0.9647
246 1.3085
247 1.6568
248 2.0092
249 2.3654
250 2.7250
251 3.0876
252 3.4528
253 3.8203
254 4.1896
255 4.5604
256 4.9322
257 5.3047
258 5.6774
259 6.0499
260 6.4219
261 6.7928
262 7.1623
263 7.5300
264 7.8954
265 8.2582
266 8.6180
267 8.9742
268 9.3265
269 9.6746
270 10.0180
271 10.3562
272 10.6890
273 11.0159
274 11.3365
275 11.6505
276 11.9574
277 12.2570
278 12.5488
279 12.8325
280 13.1078
281 13.3742
282 13.6316
283 13.8795
284 14.1176
285 14.3457
286 14.5634
287 14.7705
288 14.9668
289 15.1518
290 15.3254
291 15.4874
292 15.6375
293 15.7756
294 15.9013
295 16.0145
296 16.1152
297 16.2029
298 16.2778
299 16.3395
300 16.3880
301 16.4232
302 16.4450
303 16.4532
304 16.4479
305 16.4290
306 16.3964
307 16.3502
308 16.2903
309 16.2167
310 16.1294
311 16.0285
312 15.9141
313 15.7862
314 15.6448
315 15.4902
316 15.3223
317 15.1413
318 14.9474
319 14.7406
320 14.5212
321 14.2894
322 14.0453
323 13.7891
324 13.5211
325 13.2414
326 12.9504
327 12.6483
328 12.3353
329 12.0117
330 11.6779
331 11.3340
332 10.9805
333 10.6177
334 10.2459
335 9.8653
336 9.4765
337 9.0797
338 8.6753
339 8.2637
340 7.8453
341 7.4204
342 6.9895
343 6.5530
344 6.1112
345 5.6646
346 5.2137
347 4.7588
348 4.3003
349 3.8388
350 3.3746
351 2.9082
352 2.4400
353 1.9704
354 1.5000
355 1.0291
356 0.5583
357 0.0878
358 -0.3817
359 -0.8499
360 -1.3164
361 -1.7806
362 -2.2422
363 -2.7008
364 -3.1558
365 -3.6069
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