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

JanFebMarAprMayJunJulAugSepOctNovDec
JanFebMarAprMayJunJulAugSepOctNovDec
1326091121152182213244274305335
2336192122153183214245275306336
3346293123154184215246276307337
4356394124155185216247277308338
5366495125156186217248278309339
6376596126157187218249279310340
7386697127158188219250280311341
8396798128159189220251281312342
9406899129160190221252282313343
104169100130161191222253283314344
114270101131162192223254284315345
124371102132163193224255285316346
134472103133164194225256286317347
144573104134165195226257287318348
154674105135166196227258288319349
164775106136167197228259289320350
174876107137168198229260290321351
184977108138169199230261291322352
195078109139170200231262292323353
205179110140171201232263293324354
215280111141172202233264294325355
225381112142173203234265295326356
235482113143174204235266296327357
245583114144175205236267297328358
255684115145176206237268298329359
265785116146177207238269299330360
275886117147178208239270300331361
285987118148179209240271301332362
29 88119149180210241272302333363
30 89120150181211242273303334364
31 90 151 212243 304 365

Leap Year

JanFebMarAprMayJunJulAugSepOctNovDec
JanFebMarAprMayJunJulAugSepOctNovDec
1326192122153183214245275306336
2336293123154184215246276307337
3346394124155185216247277308338
4356495125156186217248278309339
5366596126157187218249279310340
6376697127158188219250280311341
7386798128159189220251281312342
8396899129160190221252282313343
94069100130161191222253283314344
104170101131162192223254284315345
114271102132163193224255285316346
124372103133164194225256286317347
134473104134165195226257287318348
144574105135166196227258288319349
154675106136167197228259289320350
164776107137168198229260290321351
174877108138169199230261291322352
184978109139170200231262292323353
195079110140171201232263293324354
205180111141172202233264294325355
215281112142173203234265295326356
225382113143174204235266296327357
235483114144175205236267297328358
245584115145176206237268298329359
255685116146177207238269299330360
265786117147178208239270300331361
275887118148179209240271301332362
285988119149180210241272302333363
296089120150181211242273303334364
30 90121151182212243274304335365
31 91 152 213244 305 366