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
To the young, highborn, brilliant officer, who was confessedly the real means of ending the vexatious Numidian war, the most splendid career now lay open; he took part also in the Cimbrian war, and manifested his singular talent for organization in the management of the difficult task of providing supplies; yet even now the pleasures of life in the capital had far more attraction for him than war or even politics. During his praetorship, which office he held in 661 after having failed in a previous candidature, it once more chanced that in his province, the least important of all, the first victory over king Mithradates and the first treaty with the mighty Arsacids, as well as their first humiliation, occurred.
The Civil war followed. It was Sulla mainly, who decided the first act of it--the Italian insurrection-- in favour of Rome, and thus won for himself the consulship by his sword; it was he, moreover, who when consul suppressed with energetic rapidity the Sulpician revolt. Fortune seemed to make it her business to eclipse the old hero Marius by means of this younger officer. The capture of Jugurtha, the vanquishing of Mithradates, both of which Marius had striven for in vain, were accomplished in subordinate positions by Sulla: in the Social war, in which Marius lost his renown as a general and was deposed, Sulla established his military repute and rose to the consulship; the revolution of 666, which was at the same time and above all a personal conflict between the two generals, ended with the outlawry and flight of Marius.
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Reference address : https://www.ellopos.net/elpenor/rome/4-10-sullan-constitution.asp?pg=66