🗓️ Day of Year Reference
The day of year (ordinal date) is the count of days from January 1. Regular years have 365 days; leap years have 366. Use this table to find the ordinal day number for any date.
Month Start Days
First day of each month as day number. Leap years shown separately (February has 29 days).
| Month | Days in Month | First Day (Regular) | Last Day (Regular) | First Day (Leap) |
|---|---|---|---|---|
| January | 31 | 1 | 31 | 1 |
| February | 28 (29 leap) | 32 | 59 | 32 |
| March | 31 | 60 | 90 | 61 |
| April | 30 | 91 | 120 | 92 |
| May | 31 | 121 | 151 | 122 |
| June | 30 | 152 | 181 | 153 |
| July | 31 | 182 | 212 | 183 |
| August | 31 | 213 | 243 | 214 |
| September | 30 | 244 | 273 | 245 |
| October | 31 | 274 | 304 | 275 |
| November | 30 | 305 | 334 | 306 |
| December | 31 | 335 | 365 | 336 |
How to Calculate Day of Year
Formula (Regular Year)
Day of Year = Month Start Day + (Day of Month - 1)
Example: March 15 in a regular year = 60 + (15 - 1) = Day 74.
Leap years (divisible by 4, except century years not divisible by 400): add 1 to the start day for March and later months. Upcoming leap years: 2024, 2028, 2032.