3 Answers

This is usually a word associated with a rule, law, or business practice.  For example, long ago, they changed the drinking age in my State from 18 yr.olds- 21 yr olds.  But they grandfathered in everyone who was already 18-21 on that date.  I for get the date but lets use April 1st.  If you had already turned 18 but were not yet 21 on April 1st you were still allowed to drink.  As of April 2nd and beyond you legally had to wait until you were 21 years old to drink.  Another example would be a business that wants to stop supplying workers with pensions.  They could announce that On Jan 1st 2012 no new employee will receive a pension but they will grandfather in all existing employees- meaning if you already work there you will receive some $ as a pension.

In zoning, something that is grandfathered in, was before the zoning changed, as an example:

A person living in aa commercial zone, although when they built there it was an R-1 residential zone.

Tthe government may allow them to continue living there, as residential, but they are now living in a commericail zone-meaning they have all the rights for the new zoning, such as starting a store from their house.  there are many grandfathered zoning issues of similarity..

It means if you were doin somethin when the ae was okay and you were that age then the Law change you can still do it.!