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# Day of the Year (DOY) calendar

Some data sets specify dates using the year and day of year rather than the year, month, and day of month. The day of year (DOY) is the sequential day number starting with day 1 on January 1st.

There are two calendars--one for normal years with 365 days, and one for leap years with 366 days. Leap years are divisible by 4. Centuries, like 1900, are not leap years unless they are divisible by 400. So, 2000 was a leap year.

To find the day of year number for a standard date, scan down the Jan column to find the day of month, then scan across to the appropriate month column and read the day of year number. Reverse the process to find the standard date for a given day of year.

The day of year number is sometimes referred to as the "Julian" date, but astronomers have a very specific definition of Julian Date.

## Normal Year

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
1 32 60 91 121 152 182 213 244 274 305 335
2 33 61 92 122 153 183 214 245 275 306 336
3 34 62 93 123 154 184 215 246 276 307 337
4 35 63 94 124 155 185 216 247 277 308 338
5 36 64 95 125 156 186 217 248 278 309 339
6 37 65 96 126 157 187 218 249 279 310 340
7 38 66 97 127 158 188 219 250 280 311 341
8 39 67 98 128 159 189 220 251 281 312 342
9 40 68 99 129 160 190 221 252 282 313 343
10 41 69 100 130 161 191 222 253 283 314 344
11 42 70 101 131 162 192 223 254 284 315 345
12 43 71 102 132 163 193 224 255 285 316 346
13 44 72 103 133 164 194 225 256 286 317 347
14 45 73 104 134 165 195 226 257 287 318 348
15 46 74 105 135 166 196 227 258 288 319 349
16 47 75 106 136 167 197 228 259 289 320 350
17 48 76 107 137 168 198 229 260 290 321 351
18 49 77 108 138 169 199 230 261 291 322 352
19 50 78 109 139 170 200 231 262 292 323 353
20 51 79 110 140 171 201 232 263 293 324 354
21 52 80 111 141 172 202 233 264 294 325 355
22 53 81 112 142 173 203 234 265 295 326 356
23 54 82 113 143 174 204 235 266 296 327 357
24 55 83 114 144 175 205 236 267 297 328 358
25 56 84 115 145 176 206 237 268 298 329 359
26 57 85 116 146 177 207 238 269 299 330 360
27 58 86 117 147 178 208 239 270 300 331 361
28 59 87 118 148 179 209 240 271 301 332 362
29   88 119 149 180 210 241 272 302 333 363
30   89 120 150 181 211 242 273 303 334 364
31   90   151   212 243   304   365
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

## Leap Year

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
1 32 61 92 122 153 183 214 245 275 306 336
2 33 62 93 123 154 184 215 246 276 307 337
3 34 63 94 124 155 185 216 247 277 308 338
4 35 64 95 125 156 186 217 248 278 309 339
5 36 65 96 126 157 187 218 249 279 310 340
6 37 66 97 127 158 188 219 250 280 311 341
7 38 67 98 128 159 189 220 251 281 312 342
8 39 68 99 129 160 190 221 252 282 313 343
9 40 69 100 130 161 191 222 253 283 314 344
10 41 70 101 131 162 192 223 254 284 315 345
11 42 71 102 132 163 193 224 255 285 316 346
12 43 72 103 133 164 194 225 256 286 317 347
13 44 73 104 134 165 195 226 257 287 318 348
14 45 74 105 135 166 196 227 258 288 319 349
15 46 75 106 136 167 197 228 259 289 320 350
16 47 76 107 137 168 198 229 260 290 321 351
17 48 77 108 138 169 199 230 261 291 322 352
18 49 78 109 139 170 200 231 262 292 323 353
19 50 79 110 140 171 201 232 263 293 324 354
20 51 80 111 141 172 202 233 264 294 325 355
21 52 81 112 142 173 203 234 265 295 326 356
22 53 82 113 143 174 204 235 266 296 327 357
23 54 83 114 144 175 205 236 267 297 328 358
24 55 84 115 145 176 206 237 268 298 329 359
25 56 85 116 146 177 207 238 269 299 330 360
26 57 86 117 147 178 208 239 270 300 331 361
27 58 87 118 148 179 209 240 271 301 332 362
28 59 88 119 149 180 210 241 272 302 333 363
29 60 89 120 150 181 211 242 273 303 334 364
30   90 121 151 182 212 243 274 304 335 365
31   91   152   213 244   305   366
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
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