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-Feb (Gregorian Calendar) Local Time Zone Offset : -05:00 (-West) Daylight/Summer Time : No ---------------------------------------------- TABLE OF CALENDAR DATES OF MOON QUARTER PHASES AD 2026-Feb-01 Full Moon AD 2026-Feb-09 Last Quarter AD 2026-Feb-17 New Moon AD 2026-Feb-24 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 2026-Jan-31 00:00:00 Gem 2461071.708333333 157.16139 AD 2026-Feb-01 00:00:00 Cnc 2461072.708333333 170.56154 AD 2026-Feb-02 00:00:00 Cnc 2461073.708333333 183.72588 AD 2026-Feb-03 00:00:00 Leo 2461074.708333333 196.57483 AD 2026-Feb-04 00:00:00 Leo 2461075.708333333 209.05981 AD 2026-Feb-05 00:00:00 Vir 2461076.708333333 221.16627 AD 2026-Feb-06 00:00:00 Vir 2461077.708333333 232.91126 AD 2026-Feb-07 00:00:00 Vir 2461078.708333333 244.33764 AD 2026-Feb-08 00:00:00 Vir 2461079.708333333 255.50703 AD 2026-Feb-09 00:00:00 Lib 2461080.708333333 266.49292 AD 2026-Feb-10 00:00:00 Lib 2461081.708333333 277.37465 AD 2026-Feb-11 00:00:00 Sco 2461082.708333333 288.23226 AD 2026-Feb-12 00:00:00 Oph 2461083.708333333 299.14211 AD 2026-Feb-13 00:00:00 Sgr 2461084.708333333 310.17313 AD 2026-Feb-14 00:00:00 Sgr 2461085.708333333 321.38343 AD 2026-Feb-15 00:00:00 Sgr 2461086.708333333 332.81744 AD 2026-Feb-16 00:00:00 Cap 2461087.708333333 344.50390 AD 2026-Feb-17 00:00:00 Cap 2461088.708333333 356.45491 AD 2026-Feb-18 00:00:00 Aqr 2461089.708333333 8.66660 AD 2026-Feb-19 00:00:00 Psc 2461090.708333333 21.12123 AD 2026-Feb-20 00:00:00 Psc 2461091.708333333 33.79070 AD 2026-Feb-21 00:00:00 Psc 2461092.708333333 46.64051 AD 2026-Feb-22 00:00:00 Ari 2461093.708333333 59.63342 AD 2026-Feb-23 00:00:00 Ari 2461094.708333333 72.73189 AD 2026-Feb-24 00:00:00 Tau 2461095.708333333 85.89895 AD 2026-Feb-25 00:00:00 Tau 2461096.708333333 99.09751 AD 2026-Feb-26 00:00:00 Tau 2461097.708333333 112.28887 AD 2026-Feb-27 00:00:00 Gem 2461098.708333333 125.43122 AD 2026-Feb-28 00:00:00 Cnc 2461099.708333333 138.47932 AD 2026-Mar-01 00:00:00 Cnc 2461100.708333333 151.38581 ============== ======== ==== ================= ========= 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)