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Select a measurement and convert between different units
Single conversion
To convert from Day (d) to Year (year), use the following formula:
Let's convert 5 Day (d) to Year (year).
Using the formula:
Therefore, 5 Day (d) is equal to Year (year).
Here are some quick reference conversions from Day (d) to Year (year):
| Days | Years |
|---|---|
| 0.000001 d | year |
| 0.001 d | year |
| 0.1 d | year |
| 1 d | year |
| 2 d | year |
| 3 d | year |
| 4 d | year |
| 5 d | year |
| 6 d | year |
| 7 d | year |
| 8 d | year |
| 9 d | year |
| 10 d | year |
| 20 d | year |
| 30 d | year |
| 40 d | year |
| 50 d | year |
| 100 d | year |
| 1000 d | year |
| 10000 d | year |
The 24-hour day is the most basic unit we use to organize our lives. But what exactly defines a day, and is it always the same length?
A standard solar day, on which our clocks are based, is the time it takes for the Earth to rotate so that the Sun appears in the same position in the sky. This works out to be 86,400 seconds.
However, the story of a day is a bit more complex.
While we live by the 24-hour solar day, Earth's true rotation period is slightly shorter.
A sidereal day is the time it takes for Earth to rotate 360 degrees on its axis relative to distant stars. This period is actually 23 hours, 56 minutes, and 4 seconds.
So why is the solar day we use about four minutes longer? It's because while the Earth is spinning, it's also orbiting the Sun. After one full rotation (a sidereal day), it has to spin a little bit extra to "catch up" and bring the Sun back to the same point in the sky. That extra rotation time gives us our 24-hour solar day.
Yes, but don't adjust your watch just yet! The length of a day on Earth is slowly increasing.
This is due to a process called tidal braking, where the Moon's gravitational pull creates a slight drag on our planet's rotation, slowing it down.
This effect is minimal, adding only about 1.7 milliseconds to the length of a day every century. Although you may not notice it, it adds up over geological time. For example, when dinosaurs lived, a day on Earth was approximately 23 hours long.
Even though our clocks run on a steady 24-hour cycle, the actual length of a solar day (from one noon to the next) varies slightly throughout the year. The 24-hour day is just an average.
Two main factors cause this variation:
A year is the time it takes for the Earth to complete one full orbit around the Sun.
We commonly think of a year as 365 days, but it's not quite that simple. The Earth's journey actually takes a little longer, which is why our calendar needs a special trick to stay accurate.
The Earth takes approximately 365.24 days to travel around the Sun. That extra quarter of a day might not seem like much, but it adds up over time.
To keep our calendar in sync with the Earth's orbit and the seasons, we add an extra day—February 29th—nearly every four years. This is called a leap year.
Without leap years, our calendar would drift by about 24 days every 100 years, and eventually, we'd have summer in December!
Yes! While our calendar uses a 365-day system, scientists use more precise measurements depending on what they're tracking.
The two most common types of years are:
The idea of a "year" can get much, much bigger. Just as the Earth orbits the Sun, our entire solar system orbits the center of the Milky Way galaxy.
This enormous journey is called a Galactic Year (or cosmic year), and it takes an estimated 230 million Earth years to complete. To put that in perspective, the last time our solar system was in this exact spot, dinosaurs were beginning to roam the Earth during the Triassic period.