The day of the year calculator is an handy to compute the numerical position of a specific date within a calendar year, between 1 and 365 (or 366 for leap years).
The day of the year, also known as the Julian day number, is a sequential count of days starting from January 1st, with January 1st being day 1 and December 31st being day 365 (or 366 in a leap year). This method of counting days is widely used in various fields, including astronomy, computer programming, and logistics.
For example:
- January 1st is always the 1st day of the year.
- December 31st is the 365th day in a non-leap year.
- February 29th is the 60th day in a leap year.
Day of the Year Calculator
| Date | Non-Leap Year | Leap Year |
|---|---|---|
| January 1 | 1 | 1 |
| January 15 | 15 | 15 |
| January 31 | 31 | 31 |
| February 1 | 32 | 32 |
| February 14 | 45 | 45 |
| February 28 | 59 | 60 |
| February 29 | N/A | 60 |
| March 1 | 60 | 61 |
| March 15 | 74 | 75 |
| April 1 | 91 | 92 |
| April 15 | 105 | 106 |
| May 1 | 121 | 122 |
| May 15 | 135 | 136 |
| June 1 | 152 | 153 |
| June 15 | 166 | 167 |
| July 1 | 182 | 183 |
| July 4 | 185 | 186 |
| August 1 | 213 | 214 |
| August 15 | 227 | 228 |
| September 1 | 244 | 245 |
| September 15 | 258 | 259 |
| September 22 | 265 | 266 |
| September 30 | 273 | 274 |
| October 1 | 274 | 275 |
| October 15 | 288 | 289 |
| November 1 | 305 | 306 |
| November 15 | 319 | 320 |
| December 1 | 335 | 336 |
| December 15 | 349 | 350 |
| December 25 | 359 | 360 |
| December 31 | 365 | 366 |
- January: The first month of the year starts with January 1 as the 1st day and ends with January 31 as the 31st day.
- February: In a non-leap year, it has 28 days, while in a leap year, it includes February 29, making it the 60th day of the year.
- March to December: The table continues through the months, showing the cumulative total of days for both non-leap and leap years.
Day of the Year Calculation Formula
For a non-leap year:
Day of Year = (153 * m + 2) / 5 + d + n
Where:
- m = month number (3 for March, 4 for April, …, 14 for February)
- d = day of the month
- n = -91 if m < 3, otherwise -90
For leap years, add 1 to the result if the date is after February 29th.
Day of the Year = (Month × 30.4) – (30.4 – Day)
How do you calculate the day of the year?
- Identify the month and day: Determine the month and day of the date you want to calculate.
- Apply the formula: Plug the month and day into the formula: Day of the Year = (Month × 30.4) – (30.4 – Day).
- Round the result: Round the result to the nearest whole number to get the day of the year.
For example, let’s calculate the day of the year for April 22nd:
- Month = 4
- Day = 22
- Day of the Year = (4 × 30.4) – (30.4 – 22) = 121.6 (rounded to 122)
What is the 273rd day of the year?
- Count through completed months:
- January (31) + February (28) + March (31) + April (30) + May (31) + June (30) + July (31) + August (31) = 243 days.
- The remaining 30 days fall in September.
- 273 – 243 = 30.
the 273rd day of a non-leap year is September 30th.
In a leap year, it would be September 29th due to the extra day in February.
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