The usual designation for the sabbath day in Greek is "the day of the Sabbaths," and in Hebrew "the day of the Sabbath" (hemera twv sabbatwn & Yom HaShabbat).  The grammar of the resurrection passages implies the word "day," hence the full form is "first [day] of the Sabbaths."  This is to be compared with the three texts for the feast of unleavened bread, viz. Luke 22:7, "Came yet the day of the unleavens," (which is like "day of the sabbaths") and Matthew 26:17, "The yet first of the unleavens" (which is like "first of the Sabbaths), and Mk. 14:12, "And on the first day of the unleavens."  Luke 22:7, Matthew 26:17, and Mk. 14:12 all mean exactly the same day.  All the grammatical genders and numbers of these passages are exactly parallel to the grammar and  gender constructs of the resurrection passages.  They show that by placing a numeral before "of the Sabbaths," or "day of the Sabbaths" does not convert the day to any other day.  The numeral only counts that day.      The passages cannot be read "first day [from] the Sabbath" because the Yehudim never counted days "from" the Sabbath.  If they mentioned the Sabbath.  They counted days "to" the Sabbath.  The Greek, however, cannot mean "to" the Sabbath.  The genitive case does not have that meaning.  Neither can the word Sabbath mean "week" in these passages, because as is shown from the examples above, adding "first" to the phrase does not convert it to any other day.  Prior usage forces us to understand the meaning as "first Sabbath day."