You might be interested in perusing the wikipedia entry on the present subjunctive in English.
The main relevant part here is:
The form is called the present subjunctive because it resembles the present indicative in form, not because it need refer to the present time. In fact this form can equally well be used in sentences referring to past, future or hypothetical time (the time frame is normally expressed in the verb of the main clause).
IOW, in English we often use the form of the present subjunctive to refer to hypotheticals (eg: perhaps breaking someone's limbs), regardless of time.