Just realised that for some reason I have never played as the Aztecs.
So... when I build a Sacrificial Altar, does it reduce the duration of already existing whip anger in the city, or only new anger from whipping after the Sacrificial Altar is built?
Cuts remaining duration in half. Note that it does not cut unhappiness in half, just the duration. From then on, unhappiness disappears at a rate of 1/15 turns instead of 1/30 turns (marathon numbers)