Daniel 9:24-26 (YLT):
weeks[sevens] are determined for thy people, and for thy holy city, to shut up the transgression, and to seal up sins, and to cover iniquity, and to bring in righteousness age-during[ancient justice], and to seal up vision and prophet, and to anoint the holy of holies.
And thou dost know, and dost consider wisely, from the going forth of the word to restore and to build Jerusalem till
Messiah the Leader[anointed prince] is seven weeks[sevens], and sixty and two weeks[sevens]: the broad place hath been built again, and the rampart, even in the distress of the times.
And after the sixty and two
weeks[sevens], cut off is Messiah[anointed], and the city and the holy place are not his[and he has not], the Leader who hath come doth destroy the people; and its end is with a flood, and till the end is war, determined are desolations.
According to this answer to another question the 'weeks' would be more accurate if they were translated as 'sevens'.
2Chronicles 36:20-21 seems to imply these sevens refer to land sabbath cycles:
And he removeth those left of the sword unto Babylon, and they are to him and to his sons for servants, till the reigning of the kingdom of Persia,
to fulfil the word of Jehovah in the mouth of Jeremiah, till the land hath enjoyed its sabbaths; all the days of the desolation it kept sabbath -- to the fulness of seventy years.
This squares with what is recorded in Leviticus 26:27-35:
'And if for this ye hearken not to Me, and have walked with Me in opposition,
then I have walked with you in the fury of opposition, and have chastised you, even I, seven times for your sins.
'And ye have eaten the flesh of your sons; even flesh of your daughters ye do eat.
And I have destroyed your high places, and cut down your images, and have put your carcases on the carcases of your idols, and My soul hath loathed you;
and I have made your cities a waste, and have made desolate your sanctuaries, and I smell not at your sweet fragrances;
and I have made desolate the land, and your enemies, who are dwelling in it, have been astonished at it.
And you I scatter among nations, and have drawn out after you a sword, and your land hath been a desolation, and your cities are a waste.
'Then doth the land enjoy its sabbaths -- all the days of the desolation, and ye in the land of your enemies -- then doth the land rest, and hath enjoyed its sabbaths;
all the days of the desolation it resteth that which it hath not rested in your sabbaths in your dwelling on it.
This is also the same subject matter that Daniel was reading about at the beginning of Daniel 9:
In the first year of Darius, son of Ahasuerus, of the seed of the Medes, who hath been made king over the kingdom of the Chaldeans,
in the first year of his reign, I, Daniel, have understood by books the number of the years, (in that a word of Jehovah hath been unto Jeremiah the prophet,) concerning the fulfilling of the wastes of Jerusalem -- seventy years;
The context implies these sevens refer to land sabbath cycles of 7 years, but is there anything more explicit in the text of Daniel 9:24-26 that explains which units of seven these 'sevens' refer to? Is it days? Weeks? Months? Years?