Off the clock. I can't speak for commonplace, this specific agreement was from 1999 and was probably not enforceable then (but who knows) as I believe no one can reasonably be expected to turn over original creations and impoverish themselves, if there is no connection to the company's area of business. Things vary depending on the year and the country.

You can negotiate your agreements if you see something objectionable in them. (Read them!)