Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
From: The History of Rome, by Theodor Mommsen
Translated with the sanction of the author by William Purdie Dickson
It was the time-honoured maxim by which the senate had at one time made the monarchy subject to it, that the limitation of the magistracy in point of function was favourable to democracy, and its limitation in point of time favourable to oligarchy. According to the previous arrangement Gaius Marius had acted at once as head of the senate and as commander-in-chief of the state; if he had his own unskilfulness alone to blame for his failure to overthrow the oligarchy by means of this double official power, care seemed now taken to prevent some possibly wiser successor from making a better use of the same lever.
According to the previous arrangement the magistrate immediately nominated by the people might have had a military position; the Sullan arrangement, on the other hand, reserved such a position exclusively for those magistrates whom the senate confirmed in their official authority by prolonging their term of office. No doubt this prolongation of office had now become a standing usage; but it still--so far as respects the auspices and the name, and constitutional form in general--continued to be treated as an extraordinary extension of their term.
This was no matter of indifference. The burgesses alone could depose the consul or praetor from his office; the proconsul and propraetor were nominated and dismissed by the senate, so that by this enactment the whole military power, on which withal everything ultimately depended, became formally at least dependent on the senate.
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Reference address : https://www.ellopos.net/elpenor/rome/4-10-sullan-constitution.asp?pg=40