Sidereal Time Calculator For Any Date, Time and Longitude
PHP Program by Jay Tanner
Local Date
±
Y M D (Neg=BC)
Local Time
HH MM SS (00 to 24h)
Local Time Zone Offset
HH MM (Neg/Pos = W/E)
ΔT (Delta T)
±
HMS
UT
2461303.5
0.868240740741
-0.208333333333
+0.000000000000
Calendar Mode:
Julian
Gregorian
Longitude:
±Deg.ddd or ±D M S (Neg=W)
-76.8233097222
IMPORTANT:
Make sure that the local time, time zone and longitude are correctly matched for the location.
OPTIONAL:
NASA Polynomial ΔT estimate = +76 sec = +00h 01m 16s
Double-Click Within Text Area to Select ALL Text
SIDEREAL TIME FOR GIVEN DATE, TIME AND LONGITUDE Local Date = 2026 Sep 20 [Sunday] Gregorian JD Number = 2461304 JD00 = 2461303.5 = JD for 00h of date Local Time = 20:50:16 = 0.868240740741 day T Zone Diff = -05:00 = -0.208333333333 day Delta T = +00:00:00 = +0.000000000000 day Astronomical Julian Date: JDTT = JDNum - 0.5 + LTFrac - (TZFrac) + (dTFrac) = 2461304.576574074074 Longitude = -76° 49' 23.915" = -76.8233097222° (W) = -05h 07m 17.594s = -5.1215539815 h ================================================================= Local Mean Sidereal Time at Longitude -76.8233097222° (W) 20h 42m 49.188s = 20.7136632912 h 310° 42' 17.82" = 310.7049493683° Local True Sidereal Time at Longitude = -76.8233097222° (W) 20h 42m 49.736s = 20.7138155876 h 310° 42' 26.04" = 310.7072338147° Greenwich Mean Sidereal Time 01h 50m 06.782s = 1.8352172727 h 27° 31' 41.733" = 27.5282590906° Greenwich True Sidereal Time 01h 50m 07.330s = 1.8353695691 h 27° 31' 49.957" = 27.5305435371° ================================================================= Applied Auxiliary Computations Time Factors Corresponding to Full Astronomical JD T = 0.267202644054 Julian centuries reckoned from J2000.0 t = 0.026720264405 Julian millennia reckoned from J2000.0 Circular Trig Functions of Given Longitude Longitude = -76.8233097222° (W) sin(Lon) = -0.973671722605411 cos(Lon) = +0.227954768756023 tan(Lon) = -4.271337370649689 Nutations (IAU 2000B Series) +8.964" = +0.0024898865° = Nutation in ecliptical longitude +8.282" = +0.0023005616° = Nutation in ecliptical obliquity +0.548s = +0.0022844465° = Equation of the equinoxes Mean Ecliptic Obliquity 23° 26' 08.940" = 23.4358167940° Nutation in Obliquity +8.282" = +0.0023005616° True Ecliptic Obliquity 23° 26' 17.222" = 23.4381173556°
Jay Tanner - PHP Science Labs - 2026 - 1.7