Convertir cadenas a la fecha, formatear: "dd.mm.aaaa"

Question

D <- "06.12.1948"     # which is dd.mm.yyyy 
as.Date(D, "%d.%m.%y")   # convert to date 
[1] "2019-12-06"     # ????  

¿Qué es lo que me falta?

Sys.getlocale (categoría = "LC_ALL") [1] "LC_COLLATE = German_Austria.1252; LC_CTYPE = German_Austria.1252; LC_MONETARY = German_Austria.1252; LC_NUMERIC = C; LC_TIME = German_Austria.1252"

Answer 1

El formato de mayúsculas y minúsculas ("% y" es ambiguo y depende del sistema, creo):

as.Date(D, "%d.%m.%Y") 
[1] "1948-12-06" 

El tema de ayuda ?strptime tiene detalles:

‘%y’ Year without century (00-99). On input, values 00 to 68 are 
     prefixed by 20 and 69 to 99 by 19 - that is the behaviour 
     specified by the 2004 and 2008 POSIX standards, but they do 
     also say ‘it is expected that in a future version the default 
     century inferred from a 2-digit year will change’.