title: How to add breeding season column generated from "date" column
body: <p>I have datapoints of locations of nests, and each datapoint has a column with the date (dd/MM/yyyy) it was found. I want to generate another column that says which breeding season this nest was found (and a breeding season begins in one year and ends in the next).</p>
  <p>So if a nest was found in the first half of the year, then it is in the breeding season for that year and the one prior. Alternatively, if the nest was found in the second half of the year (June onwards), then the breeding season is that year and the following year.</p>
  <p>For example, datapoint recorded on 25/04/2016 will be breeding season &quot;2015-2016&quot;, whereas datapoint on 23/11/2018 will be breeding season &quot;2018-2019&quot;.</p>
  <p>For reference, I have datapoints extending from end of 2015 (i.e. 2015-2016 breeding season) to beginning of 2021 (i.e. 2020-2021).</p>
  <p>What formula can I use in R to generate this column - if possible at all?</p>
  <p>Ive given a sample of my data (+ my desired &quot;breeding season&quot; column). Highlighted in green are the instances where the breeding season represents the year and the year preceding, blue are the breeding seasons going from the end of the year to the following year. I'd like to generate an R code that can create this &quot;Breeding season&quot; column for me automatically.</p>
  <p><a href="https://i.stack.imgur.com/AbxGO.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/AbxGO.png" alt="Example data" /></a></p>