Much ado is made about the youngest players to obtain the GM rating, but not often do we hear about the oldest. Wikipedia's list of grandmasters (see It's Official: 180 GMs by 1978 for background) has date-of-birth and date-of-title for 1099 GMs. This allows to calculate an approximate age when the title was obtained. Some of the data is inaccurate; for example, the calculation for Helgi Gretarsson has him earning the title at 8 years old. With that in mind, here is a list of oldest GMs to have obtained the title. The last column is the calculated age.
I imagine that most, if not all, of these players earned honorary GM titles. Anyone know of an exception?