Day (d)
The day is a unit of time, used for calendars, project deadlines, shipping estimates, and biological rhythms. Its symbol is d.
d
min
1 day equals
| Minutes | 1,440 min |
| Hours | 24 h |
| Seconds | 86,400 s |
About the day
The day is based on Earth's rotation period. The civil day of 24 hours was established by ancient Egyptians. A mean solar day is actually 24 hours, 0 minutes, and 0.002 seconds.
In everyday use the day appears in calendars, project deadlines, shipping estimates, and biological rhythms. As a point of reference: the International Space Station orbits Earth about 16 times per day.