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 - 2026
Date
Time Zone
Daylight/Summer Time
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MOON PHASE ANGLES AND QUARTER PHASE DATES Ephemeris Span: BC 9999-Apr to AD 9999-Nov Local Calendar Date : AD 2026-May (Gregorian Calendar) Local Time Zone Offset : -05:00 (-West) Daylight/Summer Time : No ---------------------------------------------- TABLE OF CALENDAR DATES OF MOON QUARTER PHASES AD 2026-May-01 Full Moon AD 2026-May-09 Last Quarter AD 2026-May-16 New Moon AD 2026-May-23 First Quarter AD 2026-May-31 Full Moon ----------------------------------------------------------- TABLE OF SIMPLE MOON PHASE ANGLES FOR 00:00 ON EACH DATE =========================================================== Loc_Date Loc_Time Cnst Julian_Date_UT Phase_Ang ============== ======== ==== ================= ========= AD 2026-Apr-30 00:00:00 Vir 2461160.708333333 162.94542 AD 2026-May-01 00:00:00 Vir 2461161.708333333 174.22699 AD 2026-May-02 00:00:00 Lib 2461162.708333333 185.38500 AD 2026-May-03 00:00:00 Lib 2461163.708333333 196.43625 AD 2026-May-04 00:00:00 Sco 2461164.708333333 207.40135 AD 2026-May-05 00:00:00 Oph 2461165.708333333 218.30865 AD 2026-May-06 00:00:00 Sgr 2461166.708333333 229.19717 AD 2026-May-07 00:00:00 Sgr 2461167.708333333 240.11820 AD 2026-May-08 00:00:00 Sgr 2461168.708333333 251.13536 AD 2026-May-09 00:00:00 Cap 2461169.708333333 262.32308 AD 2026-May-10 00:00:00 Cap 2461170.708333333 273.76307 AD 2026-May-11 00:00:00 Aqr 2461171.708333333 285.53855 AD 2026-May-12 00:00:00 Aqr 2461172.708333333 297.72547 AD 2026-May-13 00:00:00 Psc 2461173.708333333 310.38029 AD 2026-May-14 00:00:00 Psc 2461174.708333333 323.52517 AD 2026-May-15 00:00:00 Ari 2461175.708333333 337.13303 AD 2026-May-16 00:00:00 Ari 2461176.708333333 351.11824 AD 2026-May-17 00:00:00 Tau 2461177.708333333 5.33942 AD 2026-May-18 00:00:00 Tau 2461178.708333333 19.61853 AD 2026-May-19 00:00:00 Gem 2461179.708333333 33.77242 AD 2026-May-20 00:00:00 Gem 2461180.708333333 47.64588 AD 2026-May-21 00:00:00 Cnc 2461181.708333333 61.13425 AD 2026-May-22 00:00:00 Cnc 2461182.708333333 74.18971 AD 2026-May-23 00:00:00 Leo 2461183.708333333 86.81389 AD 2026-May-24 00:00:00 Leo 2461184.708333333 99.04336 AD 2026-May-25 00:00:00 Leo 2461185.708333333 110.93419 AD 2026-May-26 00:00:00 Vir 2461186.708333333 122.54901 AD 2026-May-27 00:00:00 Vir 2461187.708333333 133.94800 AD 2026-May-28 00:00:00 Vir 2461188.708333333 145.18355 AD 2026-May-29 00:00:00 Lib 2461189.708333333 156.29816 AD 2026-May-30 00:00:00 Lib 2461190.708333333 167.32480 AD 2026-May-31 00:00:00 Sco 2461191.708333333 178.28935 AD 2026-Jun-01 00:00:00 Oph 2461192.708333333 189.21428 ============== ======== ==== ================= ========= 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. IMPORTANT NOTE: Make sure to use the correct Time Zone and Daylight/Summer time setting or the calendar date could be 1 day in error. Visually 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)