An Etymological Dictionary of Astronomy and Astrophysics

1. The present day, time, or age.
   

   2. The present epoch in the cosmic evolution since the → Big Bang characterizd by the → redshift  z = 0.

Etymology (EN): M.E. today, from O.E. todæge, to dæge “on (this) day,” from to “at, on” + dæge, dative of dæg “→ day.”

Etymology (PE): Emruz “today,” from Mid.Pers. imrôc, imrôz, from im “this; here” + rôz, ruz, → day.