Editing D'ni time conversion (section)

==== Algorithm 1. Gregorian Date to Julian Day Number ====

Assume a Gregorian date given as Day, Month, and Year, with optional time (on a 24-hour clock) given as Hour, Minute, and Second. All values are assumed to be integers.

A. If the era of the date is BCE, convert the year to a CE year:

<pre>    Year = -(Year - 1)</pre>

B. If the month is January or February, treat it as month 13 or 14 of the previous year. This step ensures that any leap days in the period fall at the end of a "year".

<pre>    if Month < 3 then
        Month = Month + 12
        Year = Year - 1
    end if</pre>

C. Calculate the number of whole days (WD: an integer) that have elapsed. This is the number of days accounted for by the number of years that have passed, adjusted for leap days, plus the number of days accounted for by prior months in the current year, plus the day of the current month.

<pre>    WD = Day + FIX(((153 * Month) - 457) / 5) + INT(365.25 * Year) - INT(0.01 * Year) + INT(0.0025 * Year)</pre>

D. Calculate fractional day (FD: a real number), if necessary. This is the time of day in seconds, expressed as a fraction of the total number of seconds in a day. If no time is included in the conversion, let FD = 0.

<pre>    FD = ((Hour * 3600) + (Minute * 60) + Second) / 86400</pre>

E. Calculate Julian Day (JD: a real number) as:

<pre>    JD = WD + FD</pre>