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This package contains functions for calculating dates from various Julian based calendar systems.

JulianDate[date] | Returns the Julian date for the specified Gregorian date. |

ModifiedJulianDate[date] | Returns the modified Julian date for the specified Gregorian date. |

HeliocentricCorrectionTime[date, {hour, min, sec}, {d, m, s}] | Returns the heliocentric correction time in seconds for the specified date, right ascension, and declination. |

HeliocentricJulianDate[date, {hour, min, sec}, {d, m, s}] | Returns the heliocentric Julian date |

Calculating Julian calendar dates

This loads the package

In[1]:=

Here is the Julian date for the current date.

In[2]:=

Out[2]//AccountingForm=

The modified Julian date corresponds to 2400000.5 days after day 0 of the Julian calendar. It therefore gives the number of days since midnight on November 17, 1858. The modified Julian date is still in common usage in tabulations by the U. S. Naval Observatory.

Here is the modified Julian date for the current date.

In[3]:=

Out[3]//AccountingForm=

The heliocentric Julian date is the Julian date for a specified set of sky coordinates in a heliocentric coordinate system. This is necessary to compensate for the difference in light travel time between the earth and the sun. The earth's position in its orbit changes with time and can therefore result in at most an variation in timing observations. To compensate for this, the sun is chosen as the origin of the coordinate system since its distance from the source object is more stable.

Here is the heliocentric correction time for the current date in days.

In[4]:=

Out[4]=

Here is the heliocentric Julian date for the current date.

In[5]:=

Out[5]//AccountingForm=

Created by Mathematica (October 24, 2004) |