The addition wouldn't fail; it would just not be very useful. Interval scales do support addition, which comes in handy when you want to, say, calculate the cen

The addition wouldn't fail; it would just not be very useful. Interval scales do support addition, which comes in handy when you want to, say, calculate the center of mass for interesting events. What would fail would be trying to determine the factor by which 2010 is later than 1666.