Using Find which season a particular date belongs to , I slithly change the function to add a format argument:
getSeason <- function(DATES,frmt = "%Y%m%d") {
WS <- as.POSIXct("2012-12-21", format = "%Y-%m-%d") # Winter
SE <- as.POSIXct("2012-3-21", format = "%Y-%m-%d") # Spring
SS <- as.POSIXct("2012-6-21", format = "%Y-%m-%d") # Summer
FE <- as.POSIXct("2012-9-21", format = "%Y-%m-%d") # Autumn
# Convert dates from any year to 2012 dates
d <- strftime(as.POSIXct(DATES, format=frmt),
format='2012-%m-%d')
ifelse (d >= WS | d < SE, "Winter",
ifelse (d >= SE & d < SS, "Spring",
ifelse (d >= SS & d < FE, "Summer", "Fall")))
}
dayserie <- c("19790102", "19790103", "19790104", "19790105")
getSeason(dayserie,'%Y%m%d')
"Winter" "Winter" "Winter" "Winter"