Lunar Quarter Phases Dates Calculator
Ephemeris Span: BC 9999-Apr to AD 9999-Nov
Built Around the NASA/JPL Horizons API
Program by Jay Tanner - 2025
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MOON PHASE ANGLES AND QUARTER PHASE DATES Ephemeris Span: BC 9999-Apr to AD 9999-Nov Local Calendar Date : AD 2025-Sep (Gregorian Calendar) Local Time Zone Offset : -05:00 (-West) Daylight/Summer Time : No -------------------------------------- TABLE OF CALENDAR DATES OF MOON PHASES AD 2025-Aug-31 First Quarter AD 2025-Sep-07 Full Moon AD 2025-Sep-14 Last Quarter AD 2025-Sep-21 New Moon AD 2025-Sep-29 First Quarter ----------------------------------------------------------- TABLE OF SIMPLE MOON PHASE ANGLES FOR 00:00 ON EACH DATE =========================================================== Loc_Date Loc_Time Cnst Julian_Date_UT Phase_Ang ============== ======== ==== ================= ========= AD 2025-Aug-31 00:00:00 Sco 2460918.708333333 89.34970 AD 2025-Sep-01 00:00:00 Oph 2460919.708333333 100.41231 AD 2025-Sep-02 00:00:00 Sgr 2460920.708333333 111.67484 AD 2025-Sep-03 00:00:00 Sgr 2460921.708333333 123.20528 AD 2025-Sep-04 00:00:00 Sgr 2460922.708333333 135.05849 AD 2025-Sep-05 00:00:00 Cap 2460923.708333333 147.27016 AD 2025-Sep-06 00:00:00 Cap 2460924.708333333 159.85100 AD 2025-Sep-07 00:00:00 Aqr 2460925.708333333 172.78277 AD 2025-Sep-08 00:00:00 Psc 2460926.708333333 186.01737 AD 2025-Sep-09 00:00:00 Psc 2460927.708333333 199.48036 AD 2025-Sep-10 00:00:00 Psc 2460928.708333333 213.07901 AD 2025-Sep-11 00:00:00 Ari 2460929.708333333 226.71369 AD 2025-Sep-12 00:00:00 Ari 2460930.708333333 240.28992 AD 2025-Sep-13 00:00:00 Tau 2460931.708333333 253.72832 AD 2025-Sep-14 00:00:00 Tau 2460932.708333333 266.97041 AD 2025-Sep-15 00:00:00 Aur 2460933.708333333 279.97964 AD 2025-Sep-16 00:00:00 Gem 2460934.708333333 292.73855 AD 2025-Sep-17 00:00:00 Cnc 2460935.708333333 305.24394 AD 2025-Sep-18 00:00:00 Cnc 2460936.708333333 317.50161 AD 2025-Sep-19 00:00:00 Leo 2460937.708333333 329.52216 AD 2025-Sep-20 00:00:00 Leo 2460938.708333333 341.31841 AD 2025-Sep-21 00:00:00 Leo 2460939.708333333 352.90456 AD 2025-Sep-22 00:00:00 Vir 2460940.708333333 4.29694 AD 2025-Sep-23 00:00:00 Vir 2460941.708333333 15.51555 AD 2025-Sep-24 00:00:00 Vir 2460942.708333333 26.58614 AD 2025-Sep-25 00:00:00 Lib 2460943.708333333 37.54208 AD 2025-Sep-26 00:00:00 Lib 2460944.708333333 48.42561 AD 2025-Sep-27 00:00:00 Sco 2460945.708333333 59.28853 AD 2025-Sep-28 00:00:00 Oph 2460946.708333333 70.19175 AD 2025-Sep-29 00:00:00 Sgr 2460947.708333333 81.20402 AD 2025-Sep-30 00:00:00 Sgr 2460948.708333333 92.39947 AD 2025-Oct-01 00:00:00 Sgr 2460949.708333333 103.85375 ============== ======== ==== ================= ========= Loc_Date Loc_Time Cnst Julian_Date_UT Phase_Ang ===========================================================
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SEEKING THE CALENDAR DATES OF THE LUNAR PHASES Given any month within the range of the ephemeris, this program will first generate the table of lunar phase angles for 00:00 local time on each date of the given month, then it will scan the table and extract ONLY the dates of the lunar phases. The clock time of the event is NOT computed. Seeking the phase dates within the table is actually quite simple as long as we only want the calendar dates without the actual event times. We scan forward through the zero-indexed table starting at array index [1] and test the simple phase angle values in pairs to find the phase dates. Any phase occuring near the beginning of the month may possibly be repeated again near the end of the month, such as a second (blue) full moon if there is a full moon near the beginning of the month. If there are multiple similar phases, such as a blue moon or any other phase that repeats during the month, it will also be listed. --------------------------------------------------------- The table lines array is indexed from [0] and the pairing works according to this algorithm working forward from [1] up until reaching [wCount]: PrevLine = wArray[CurrIndex - 1] CurrLine = wArray[CurrIndex] ------------------------------------------------------------ The phase angle in degrees is at the end of each table line. PrevPA = Trimmed last 10 characters of raw (PrevLine). CurrPA = Trimmed last 10 characters of raw (CurrLine). When two successive values meet the test conditions, then the first of the two corresponding dates is the phase date on the calendar. ------------------------------------------------------------- Phase_Ang Phase_ID Phase Seeking Rule Within Table --------- ------------- -------------------------------- 0 New Noon (CurrPA - PrevPA) < 0 90 First Quarter (PrevPA < 90 and CurrPA >= 90) 180 Full Moon (PrevPA < 180 and CurrPA >= 180) 270 Last Quarter (PrevPA < 270 and CurrPA >= 270) ------------------------------------------------------------- Following these rules yields the moon quarter phases date table for the current given month as computed above.
PHP Program by Jay Tanner
v1.00 - Revised: 1970-January-01-Thursday at Local Time 12:00:00 AM (UTC−05:00)