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Date and Time Definitions

Date Definitions:

Modified Julian Date (MJD):

MJD = Julian Date - 2,400,000.5 days

T, the Besselian date, is given by T = 2000.000 + (MJD - 51544.03) / 365.2422

Time Definitions:

UT2-UT1 = 0.022 sin(2*pi*T) - 0.012 cos(2*pi*T) - 0.006 sin(4*pi*T) + 0.007 cos(4*pi*T)

where pi = π and T is the date in Besselian years.

  • TT = TAI + 32.184 seconds
  • since 00h 00m UTC 01 Jan 2017, the cumulative leap second count is:
    TAI-UTC = 37 seconds (exactly)
    and GPS Time-UTC = 18 seconds
  • users may compute Delta T = TT - UT1 using the relation:
         Delta T = 32.184 s + (TAI - UTC) - (UT1 - UTC)
    where
         (TAI - UTC) is the cumulative number of leap seconds
    and
         (UT1 - UTC) is a standard Earth Orientation product.

 

USNO Master Clock Time
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