mbostock/d3 — pull request #343 by johan (2011-10-18 20:42:45+00:00)
Title: Tiny prettification of the calendar examples

Non-data dates were previously showed as "NaN%" and "undefined" respectively.

This is the local fix approach. Another might be letting d3.format grow some handling for undefined, null or NaN values, say, d3.format(".01%", undefined, "N/A"); for giving a fallback for illegal input.