Determine season from Date using lubridate in R

And if you're interested in getting back four seasons, here's code to do that:

library(lubridate)
getSeason <- function(input.date){
  numeric.date <- 100*month(input.date)+day(input.date)
  ## input Seasons upper limits in the form MMDD in the "break =" option:
  cuts <- base::cut(numeric.date, breaks = c(0,319,0620,0921,1220,1231)) 
  # rename the resulting groups (could've been done within cut(...levels=) if "Winter" wasn't double
  levels(cuts) <- c("Winter","Spring","Summer","Fall","Winter")
  return(cuts)
}

Unit Test:

getSeason(as.POSIXct("2016-01-01 12:00:00")+(0:365)*(60*60*24))

I packaged @Lars Arne Jordanger's much more elegant approach into a function:

getTwoSeasons <- function(input.date){
  numeric.date <- 100*month(input.date)+day(input.date)
  ## input Seasons upper limits in the form MMDD in the "break =" option:
  cuts <- base::cut(numeric.date, breaks = c(0,415,1015,1231)) 
  # rename the resulting groups (could've been done within cut(...levels=) if "Winter" wasn't double
  levels(cuts) <- c("Winter", "Summer","Winter")
  return(cuts)
}

Testing it on some sample data seems to work fine:

getTwoSeasons(as.POSIXct("2016-01-01 12:00:00")+(0:365)*(60*60*24))

For completeness, worth noting that lubridate now has a quarter (and a semester) function. quarter splits the year into fourths and semester into halves:

library(lubridate)

quarter(x, with_year = FALSE, fiscal_start = 1)
semester(x, with_year = FALSE)

For more, see: https://www.rdocumentation.org/packages/lubridate/versions/1.7.4/topics/quarter