Recode dates

Now let's look at another dataset in the nycflights13 datasets, specifically the flights dataset. This dataset gives us the time when a particular flight departed from one of the New York City airports (JFK, LGA, EWR), it's scheduled departure and arrival times, and the departure and arrival delays. You'll begin by investigating to determine if there are any seasonal patterns for delays.

Here are the cutoff times for each season in the United States.

SPRING EQUINOX	March 20
SUMMER SOLSTICE	June 21
FALL EQUINOX	September 22
WINTER SOLSTICE	December 21

We defined the get_season() function that converts a given date to a season (one of winter, spring, summer, and fall).