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
The Budget of Expenditure
In the expenditure a diminution was in the first place obtained by the considerable restriction of the largesses of grain. The distribution of corn to the poor of the capital which was retained, as well as the kindred supply of oil newly introduced by Caesar for the Roman baths, were at least in great part charged once for all on the contributions in kind from Sardinia and especially from Africa, and were thereby wholly or for the most part kept separate from the exchequer. On the other hand the regular expenditure for the military system was increased partly by the augmentation of the standing army, partly by the raising of the pay of the legionary from 480 sesterces (5 pounds) to 900 (9 pounds) annually. Both steps were in fact indispensable.
There was a total want of any real defence for the frontiers, and an indispensable preliminary to it was a considerable increase of the army. The doubling of the pay was doubtless employed by Caesar to attach his soldiers firmly to him,(42) but was not introduced as a permanent innovation on that account.
42. Cf. V. X. Field of Caesar's Power
The former pay of 1 1/3 sesterces (3 1/4 pence) per day had been fixed in very ancient times, when money had an altogether different value from that which it had in the Rome of Caesar's day; it could only have been retained down to a period when the common day-labourer in the capital earned by the labour of his hands daily on an average 3 sesterces (7 1/2 pence), because in those times the soldier entered the army not for the sake of the pay, but chiefly for the sake of the--in great measure illicit-- perquisites of military service.
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Reference address : https://www.ellopos.net/elpenor/rome/5-11-old-republic-new-monarchy.asp?pg=81