First, thanks for the various bits of advice.

I now understand that throwing the function a days=0 does give
unexpected results (at least to those of us working off the API). So
it pays to perform a check using IF(days=0)... and/or to begin an
increasing series at 1 instead of 0 or negative numbers.

I don't believe this behavior is published anywhere or maybe it's just
me. What gives?

-- MM