Convert Year (y) to Day (Sidereal) (d (sidereal)) instantly.
About these units
Year (y)
A year is the time it takes Earth to complete one orbit around the Sun, approximately 365.2422 days. This value is not exact, which is why leap years exist. The year is the foundation of calendars, agriculture, climate cycles, financial planning, long-term engineering designs, and historical chronology. Its importance spans science, culture, religion, and economics. The modern Gregorian calendar year is an elegant compromise that aligns civil life with astronomical reality, minimizing drift between the calendar and the seasons. Despite its complexity, it remains the global standard for structuring long-term human activity.
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.