title: U.S. Naval Base Subic Bay
context: On 8 March 1885, the Spanish Navy authorized construction of the Arsenal de Olongapo and by the following September, work started at Olongapo.  Both the harbor and its inner basin were dredged and a drainage canal was built, as the Spanish military authorities were planning to make Olongapo and their navy yard an "island."  This canal also served as a line of defense and over which the bridge at the base's Main Gate passes.  When the Arsenal was finished, the gunboats Caviteño, Santa Ana, and San Quintín were assigned for its defense. To complement these gunboats, coastal artilleries were planned for the east and west ends of the station, as well as on Grande Island.
question: When was the Naval Base Subic Bay built?
answers: 8 March 1885