Phase of the Moon - Printable Version +- HP Forums (https://www.hpmuseum.org/forum) +-- Forum: HP Software Libraries (/forum-10.html) +--- Forum: HP Prime Software Library (/forum-15.html) +--- Thread: Phase of the Moon (/thread-8556.html) Phase of the Moon - Eddie W. Shore - 06-24-2017 02:30 AM The following program calculates the approximate phase of the moon. Calculation is based on the following: 1. A base date of August 11, 1999 is used, which was a New Moon. 2. The phases of the moon cycles approximately 29.530588853 days The results is a phase indicator from 0 to 1. If the indicator is close to 0 or 1, we have a New Moon. If the indicator above 0 but below 0.5, it’s the Waxing Crescent Moon. If the indicator is about or exactly 0.5, we have a Full Moon. Finally, for an indicator from 0.5 to 1, it’s the Waning Crescent Moon. Examples: June 23, 2017: the indicator is 0.991190947 June 24, 2017: the indicator is 0.025054136 Values are approximate. HP Prime Program: MOONPHASE Input: MOONPHASE(yyyy.mmdd) Code: ``` EXPORT MOONPHASE(d) BEGIN // Moon phase // 0,1: New; 0.5: Full LOCAL t,p; t:=DDAYS(1999.0811,d); p:=FP(t/29.530588853); RETURN p; END;``` Source: “Moon Phase” voidware.