Now, not only do we have to explain Daniel's Prophecy here, but we also have to disprove the misguided attempts to explain it, and also the malicious attempts to corrupt it, so that it may be of no use.  That the Almighty intended it to be used is evident.  He would not have put it in the Prophets if He had not meant it to demonstrate something.  So we will return to our question of what a "seven" is.
        The text does not say "Seventy times seven," (which would be 490); it says "Sevens Seventy" (in that order).  The word "seven" may mean either seven of something (like weeks, seven days, or seven years), or it may mean a seventh part of something in an oridinal sense: "= ordinal, Dt. 15:9 [year of the seven]; 2 K 12:2-3 [in year seven to Yayhu]; Ezek. 30:20 [on seven [day] to the month]; Ezek. 45:20 [on seven in the month]; Gen. 7:10; I Chron. 9:25." (BAG, pg. 988). What appears to be bad grammar in English, is in fact, acceptable in Biblical Hebrew of Daniel's time, so that the number seven is like the number one.  Both can be used in an ordinal sense, i.e. "seventh," "first."¹
        Thus we may understand the text as "Sevenths Seventy," i.e. as seventy seventh parts of something.  In this case, and by precedent of Deut. 15:9, it would have to be the sabbatical year, which is the seventh part of a period of seven years.
 

        1. The MT points the first word of Daniel 9:24 as "Shavoo'iym" which is the plural of Strongs #7620, meaning "period of seven," "heptad", or "week," but if we follow the rules for forming the plurals of numbers it is not quite clear how the plural of seven would be formed so that it would not be confused with "seventy,"(shiv'im) unless it was "sheva'im" (cf. Gesenius §97f, note 2).  Since, it is unlikely that Daniel himself pointed vowels into the text, we have to allow for both the meaning "period of seven," and "sevens" (as plural of seven meaning "sevenths").  The former meaning ought not to give us too much trouble, except to result in greater imprecision in calculation of the prophecy.  For if it be 69 sabbatical years, then we fit 69 between 445 b.c.e. and 34 c.e., but if 69 sabbatic periods, then we count the sabbatic period of 452-445 inclusively.  That is, part of a sabbatic period is counted as a whole period, even though only part of it falls after the word to rebuild the city.