Would Have

The third conditional uses "would have" in the result clause. We use the third conditional to talk about an impossible future. It is impossible because we cannot go back into the past and change the conditions.

If I had seen my face up close a few years ago, I would have started to use anti-aging concoctions and devices sooner.

Third Conditional

If clause: past perfect

Result clause: would + have (not) + past participle