deleting data of a given date range.

Hi,

You haven't given any example dataset.  So,not sure about the format of the date column.
set.seed(5)
dat1<-data.frame(Date1=c("10/25/2009","11/25/2009","12/25/2009","5/10/2010","8/10/2010","9/25/2011","11/28/2011","5/3/2012"),col2=sample(1:15,8,replace=TRUE))
dat1$Date1<-as.Date(dat1$Date1,format="%m/%d/%Y") #change your date column format if it is not matching to this example.
dat2<-dat1[format(dat1$Date1,"%Y")!=2009,]
dat2
#       Date1 col2
#4 2010-05-10    5
#5 2010-08-10    2
#6 2011-09-25   11
#7 2011-11-28    8
#8 2012-05-03   13
A.K.