All persons above a specified age who, during a specified brief period of either one week or one day, were in paid employment or self-employment. Persons temporarily not at workwith or without leave should be considered to be in paid employment provided they had a formal job attachment.
For operational purposes, the notion of some work may be interpreted as work for at least one hour.
http://www.ilo.org/ilostat-files/Documents/TEM.pdf