How to work out 1 year in days
Multiply the years by 365, then add one day for every February 29 between the birth date and the 1st birthday. Leap years come every four years, except century years not divisible by 400, so a 1-year span covers 0 or 1 of them.
1 year in days
1 × 365 = 365 days
+ 0 or 1 leap days
= 365 or 366 days
+ 0 or 1 leap days
= 365 or 366 days
Exact days at the 1st birthday
Examples for different birth years. The total changes slightly depending on which leap years fall inside the span.
| Born | 1st birthday | Days old |
|---|---|---|
| January 1, 1970 | Friday, January 1, 1971 | 365 |
| January 1, 1980 | Thursday, January 1, 1981 | 366 |
| January 1, 1990 | Tuesday, January 1, 1991 | 365 |
| January 1, 2000 | Monday, January 1, 2001 | 366 |
| January 1, 2010 | Saturday, January 1, 2011 | 365 |
| January 1, 2020 | Friday, January 1, 2021 | 366 |
1 year in other units
| Unit | 1 year is |
|---|---|
| Months | 12 |
| Weeks | about 52 |
| Days | 365 or 366 |
| Hours | about 8,760 |
| Minutes | about 525,600 |
| Seconds | about 31,536,000 |
Calculate your exact age in days
Enter your birthday to see how many days old you are.
For age in years, months and days, use the Age Calculator.