I have a dataframe giving attendances at sports events
Crowd matchDate
2345 1993-01-26
4567 1993-08-01
8888 1994-03-02
1298 1994-11-07
An example of my comment.
x <- as.Date(1:1000, origin = "2000-01-01")
x <- cut(x, breaks = "quarter")
And then relabel as you please, if necessary.
labs <- paste(substr(levels(x),1,4), "/", 1:4, sep="")
x <- factor(x, labels = labs)
?cut.POSIXct
breaks
a vector of cut points or number giving the number of intervals which x is to be cut into or an interval specification, one of "sec", "min", "hour", "day", "DSTday", "week", "month", "quarter" or "year", optionally preceded by an integer and a space, or followed by "s". (For "Date" objects only interval specifications using "day", "week", "month", "quarter" and "year" are allowed.)