Convert Week (week) to Day (Sidereal) (d (sidereal)) instantly.
About these units
Week (week)
A week consists of seven days, a structure stemming from ancient Babylonian and Near Eastern traditions that associated each day with a celestial body (Sun, Moon, and five visible planets). The seven-day week spread through Judaism, Christianity, and Islam, becoming one of the world's most persistent cultural time cycles. Unlike the day, month, or year, the week has no astronomical basis—its endurance is purely cultural. Yet it organizes labor systems, religious observances, markets, and global business schedules. The survival of the week across millennia demonstrates the remarkable staying power of cultural tradition, transcending scientific revolutions, political changes, and the rise of international standardization.
Day (Sidereal) (d (sidereal))
A sidereal day is the time Earth takes to rotate exactly 360 degrees relative to the distant stars—about 23 hours, 56 minutes, 4 seconds. In contrast, the solar day is slightly longer because Earth advances in its orbit each day and must rotate extra degrees for the Sun to appear in the same position in the sky. Sidereal days are fundamental to astronomy: telescopes use sidereal time to track stars, which appear in the same position in the sky at the same sidereal moment each night. This unit anchors astronomical observation to the cosmos rather than to the Sun.