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 danger increased with every onward step, and the attack, which the princes of Kent by the orders of Cassivellaunus made on the Roman naval camp, although it was repulsed, was an urgent warning to turn back. The taking by storm of a great British tree-barricade, in which a multitude of cattle fell into the hands of the Romans, furnished a passable conclusion to the aimless advance and a tolerable pretext for returning. Cassivellaunus was sagacious enough not to drive the dangerous enemy to extremities, and promised, as Caesar desired him, to abstain from disturbing the Trinobantes, to pay tribute and to furnish hostages; nothing was said of delivering up arms or leaving behind a Roman garrison, and even those promises were, it may be presumed, so far as they concerned the future, neither given nor received in earnest.
After receiving the hostages Caesar returned to the naval camp and thence to Gaul. If he, as it would certainly seem, had hoped on this occasion to conquer Britain, the scheme was totally thwarted partly by the wise defensive system of Cassivellaunus, partly and chiefly by the unserviceableness of the Italian oared fleet in the waters of the North Sea; for it is certain that the stipulated tribute was never paid. But the immediate object--of rousing the islanders out of their haughty security and inducing them in their own interest no longer to allow their island to be a rendezvous for continental emigrants-- seems certainly to have been attained; at least no complaints are afterwards heard as to the bestowal of such protection.
Do you see any typos or other mistakes? Please let us know and correct them
Reference address : https://www.ellopos.net/elpenor/rome/5-07-subjugation-west.asp?pg=95