Julian Century

This formula calculates the Julian Century $\textit{JC}$ for a given Julian Date $\text{JD}$:

$\textit{JC} = \frac{\text{JD} - 2451545}{36525}$

The value $2451545$ corresponds to January 1, 2000, at 12:00 TT (Terrestrial Time). This date is used as the epoch (reference point) known as J2000.0.

The function subtracts the reference Julian Date (2451545.0) from the input Julian Date. This difference gives the number of days since January 1, 2000, 12:00 TT.

The result is then divided by 36525, which is the number of days in 100 Julian years ($100 \times 365.25$). This conversion factor converts the time difference into Julian Centuries.

Code Implementation

def julian_century(julian_date: float) -> float:
    # Based on J2000 epoch 
    j_c = (julian_date - 2451545.0) / 36525
    return j_c