I found an audio log from halsey in the area where you fight the hunter pair, according to it she was present on the station in December 15, 2554. In it she remarks about how the UNSC found a AI matrix compilier similiar to the one currently in use by the UNSC of which she created.
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If you're that far, than you should know that Halsey has a [i]geas[/i] that led her to create Cortana. Among other things.