Sunday times dating
Direct evidence for a more fully formed Christian festival of Pascha (Easter) begins to appear in the mid-2nd century.
Perhaps the earliest extant primary source referring to Easter is a mid-2nd-century Paschal homily attributed to Melito of Sardis, which characterizes the celebration as a well-established one.
The modern English term Easter, cognate with modern Dutch ooster and German Ostern, developed from an Old English word that usually appears in the form Ēastrun, -on, or -an; but also as Ēastru, -o; and Ēastre or Ēostre.
While martyrs' days (usually the individual dates of martyrdom) were celebrated on fixed dates in the local solar calendar, the date of Easter was fixed by means of the local Jewish lunisolar calendar.
This is consistent with the celebration of Easter having entered Christianity during its earliest, Jewish period, but does not leave the question free of doubt.
Easter therefore varies between 4 April and 8 May on the Gregorian calendar (the Julian calendar is no longer used as the civil calendar of the countries where Eastern Christian traditions predominate).
Also, because the Julian "full moon" is always several days after the astronomical full moon, the eastern Easter is often later, relative to the visible moon's phases, than western Easter.
Eastern Christianity bases its calculations on the Julian Calendar.