granny leave
n. Reduced or more flexible working hours given to a person who needs to care for an ailing or elderly parent.
Last month came the announcement that Trade and Industry Secretary Patricia Hewitt's push on flexible working time includes "granny leave" for staff who want to work fewer hours to be able to look after their parents.
—Lynne Franks, “Life's working out for baby boomers,” Sunday Express, May 09, 2004
Fathers may get up to six months' paid paternity leave and there could be a 'granny leave' law to allow several million workers who look after elderly or disabled relatives to demand flexible hours.
—Steve Doughty, “Labour will give 'family-friendly' hours to 12 million,” Daily Mail (London, England), April 06, 2004
2004 (earliest)
Staff with elderly parents to care for could win the right to work fewer hours under radical plans to help Britons juggle jobs and family life.

This 'granny leave' would give adults torn between their careers and nursing ailing parents the right to request part-time work or flexible hours, as parents of young children already can.
—Gaby Hinsliff, “'Granny leave' plan for employees,” The Observer (London, England), April 04, 2004