Day Conversion Tool - Convert Days to Any Unit
Convert Days to Other Units
Quick Conversions
Convert Other Units to Days
Quick Conversions
Related Time / Duration Units
Day Conversion Table
This comprehensive day conversion table shows how various units relate to days. Use this reference for quick conversions between days and other common time units.
| Conversion | To Unit | Multiplier |
|---|---|---|
| Days to seconds | Seconds | 86400 |
| Days to milliseconds | Milliseconds | 86400000 |
| Days to microseconds | Microseconds | 86400000000 |
| Days to nanoseconds | Nanoseconds | 86400000000000 |
| Days to picoseconds | Picoseconds | 86400000000000000 |
| Days to minutes | Minutes | 1440 |
| Days to hours | Hours | 24 |
| Days to weeks | Weeks | 0.142857 |
| Days to fortnights | Fortnights | 0.0714286 |
| Days to months | Months | 0.0328767 |
| Days to years | Years | 0.00273791 |
| Days to decades | Decades | 0.000273791 |
| Days to centuries | Centuries | 0.0000273791 |
| Days to millennia | Millennia | 0.00000273791 |
This day conversion reference table provides accurate conversion factors for various time units. All values are based on internationally recognized standards for maximum precision.
What is a Day?
The day (symbol: d) is a unit of time equal to 24 hours or 86,400 seconds. It is defined as the time it takes for the Earth to complete one rotation relative to the Sun. This period is also known as a solar day. The day is commonly used as a unit of time in calendars and everyday life.
The day is not an SI unit, but it is accepted for use with SI units. Our day conversion tool helps you easily convert between days and other units. For example, 1 day equals 24 hours or 1440 minutes.
What is the SI of Day?
The day is not an SI base unit, but it is accepted for use with SI units. The SI base unit for time is the second (s). All other time units are derived from the second:
- Minute (min) = 60 seconds
- Hour (h) = 3,600 seconds
- Day (d) = 86,400 seconds
- Week = 604,800 seconds
What are Days Used For?
Days are used in a wide range of applications in daily life, science, and commerce. As a standard unit of time measurement, days provide a convenient way to measure durations and organize schedules:
Calendar Systems
Organizing events, appointments, and tracking time in calendars. For example, a project might have a duration of 30 days.
Astronomy
Measuring planetary rotation periods and orbital periods. For example, a Martian day (sol) is approximately 1.03 Earth days.
Medicine
Tracking medication schedules, treatment durations, and patient recovery times. For example, a course of antibiotics might last 7 days.
Finance
Calculating interest periods, payment schedules, and investment durations. For example, a loan might have a 365-day term.
Etymology and History
The word "day" comes from Old English "dæg" and has cognates in many Germanic languages. The concept of a day is based on the Earth's rotation period relative to the Sun. Historically, the day was divided into 24 hours, with each hour further divided into 60 minutes and each minute into 60 seconds.
The modern definition of a day is based on the SI second, with one day defined as exactly 86,400 seconds. This definition accounts for leap seconds that are occasionally added to keep atomic time in sync with astronomical time. The use of days as a unit of time measurement dates back thousands of years and is found in virtually all cultures and civilizations.
Frequently Asked Questions
Why is a day 24 hours long?
The 24-hour day originated in ancient Egypt, where they divided daylight into 10 hours measured with devices such as shadow clocks, plus 2 twilight hours. Nighttime was similarly divided into 12 hours. This 24-hour system was later adopted by the Greeks and Romans and has persisted to the present day. The modern definition of a day as exactly 86,400 seconds is based on atomic time.
How accurate is the day definition?
The current definition of a day is extremely accurate, based on the SI second which is defined by the frequency of a cesium atomic clock. However, the Earth's rotation is gradually slowing, requiring occasional leap seconds to keep atomic time in sync with astronomical time. This ensures our clocks remain accurate with respect to the Sun's position.
What's the difference between a solar day and a sidereal day?
A solar day is the time it takes for the Sun to return to the same position in the sky (24 hours). A sidereal day is the time it takes for Earth to complete one full rotation relative to distant stars (about 23 hours and 56 minutes). The solar day is about 4 minutes longer due to Earth's orbital motion around the Sun.
How do I convert days to other units?
Use our day conversion calculators above, or multiply by the appropriate conversion factor. For example, to convert days to hours, multiply by 24; to convert days to seconds, multiply by 86,400. For detailed instructions on converting days to hours, visit our d to h converter.
What are common uses for day conversion?
Day conversion is essential in scheduling (project timelines), science (experiment durations), medicine (treatment schedules), and finance (loan terms). Whether calculating how many hours are in a work week or converting a project timeline from days to weeks, our day converter tool simplifies these everyday tasks.
How does day conversion differ from other time units?
As a commonly used unit of time, the day serves as a convenient reference point for many applications. While not an SI base unit, it is accepted for use with SI units. All other common time units can be expressed in terms of days (hour = 1/24 day, week = 7 days), making day conversion particularly intuitive.
Can I convert very small or very large time measurements in days?
Yes, our day converter handles both extremely small and large time measurements with precision. For very short durations, convert seconds to days (1 s = 1/86400 day). For long periods, convert days to years or decades. Our smart rounding feature ensures readable results for all scales.
Is your day conversion tool free to use?
Yes, our day conversion calculator is completely free with no registration required. Simply enter your value, select your target unit, and get instant, accurate results. We believe precise time measurement conversion should be accessible to everyone, from students learning about time units to professionals working on complex projects.