How days and years are converted
Use one chosen year length throughout. Months in the breakdown are average months, not calendar months.
years = days ÷ year length; days = years × year length; average month = year length ÷ 12; weeks = days ÷ 7.
- Divide days by the chosen year length to find years. Multiply years by that length to find days.
- Take out whole years, then divide the remaining days by an average month of year length divided by 12.
- Take out whole average months. The remainder is days, rounded to 4 decimal places.
- Divide the total days by 7 for the weeks equivalent. Seconds to Years Converter and Weeks to Years Converter use the same year lengths.
Worked example: 1,000 ÷ 365.2425 = 2.7379 years. The average-month breakdown is 2 years, 8 months and 26.02 days. With a 365-day year it is 2 years, 8 months and 26.6667 days, not 9 whole months.
Common day durations
| Days | Years | Years, months and days | Weeks equivalent |
|---|---|---|---|
| 100 days | 0.2738 years | 0 years, 3 months, 8.6894 days | 14.2857 weeks |
| 365 days | 0.9993 years | 0 years, 11 months, 30.1944 days | 52.1429 weeks |
| 500 days | 1.369 years | 1 year, 4 months, 13.01 days | 71.4286 weeks |
| 1,000 days | 2.7379 years | 2 years, 8 months, 26.02 days | 142.8571 weeks |
| 5,000 days | 13.6895 years | 13 years, 8 months, 8.3525 days | 714.2857 weeks |
| 10,000 days | 27.3791 years | 27 years, 4 months, 16.705 days | 1,428.5714 weeks |
Swipe the table sideways to see the rest.
These examples use the Gregorian average year and average months, not calendar dates.
Things to consider
- For an exact span between real dates, use the Days Calculator: Days Between Two Dates.
- For calendar age, use actual birth and end dates rather than an average-year conversion.
- Gregorian and Julian average years are different conventions.
Frequently asked questions
How many days are in a year?
A common calendar year has 365 days and a leap year has 366. The Gregorian average is 365.2425 days. A Julian year is exactly 365.25 days. Choose the convention that matches your duration.
Why use 365.2425 days?
The Gregorian calendar has 97 leap years in each 400-year cycle. There are 146,097 days in that cycle; dividing by 400 gives 365.2425. This average is useful for comparing durations, but an individual calendar year is still 365 or 366 days.
How do I convert days to years, months and days?
Take out whole years using the selected length. Divide the remainder by year length divided by 12 and take out whole average months. What remains is days. For 1,000 days using a 365-day year, this gives 2 years, 8 months and 26.6667 days. Calendar months have different lengths.
How many days are in 10 years?
A usual ten-year calendar span has 3,652 or 3,653 days depending on its leap years. A span crossing a century year that is not a leap year can have 3,651. Ten Gregorian average years are 3,652.425 days; ten common years are 3,650. Use the Days Calculator: Days Between Two Dates for an exact span.
How old is someone who is 10,000 days old?
10,000 days is about 27.3791 Gregorian average years. This is a duration estimate, not an exact birthday-based age. Actual age depends on the birth date and the leap days in the span.
Results are estimates for general information only, not financial, medical or professional advice.