Antonyms future*, the present, tomorrow.
Just gone by or elapsed:antecedent, anterior, earlier, foregoing, former, precedent, preceding, previous, prior. See time
Having been such previously:erstwhile, former, late, old, once, onetime, previous, quondam, sometime, whilom. See precede
Past events surrounding a person or thing:background, history. See happen
A former period of time or of one's life:yesterday, yesteryear, yore. Idioms: bygone days, days gone by, the good old days, the old days. See time