The epoch ’=J2004.5 is the date 2004 July  2.125  (JD 2453188.625)
  it corresponds to the Besselian epoch B2004.50137

                                        h  m
 Beginning of the spring March    20,  6 48.6 UT
    >>            summer June     21,  0 56.8 UT
    >>            autumn September22, 16 29.8 UT
    >>            winter December 21, 12 41.6 UT
                                           h
 The Earth at perihelion January    4,   17.7 UT
 The Earth at aphelion   July       5,   10.9 UT