Spring is commonly used in literature to represent things like birth, new beginnings, growth, etc. Overall, Spring is used to show positive themes. To best represent a nearing death and other negative themes, an author should opt to use Winter or Autumn.
There are small moments in the book that are left out of the film, like Ponyboy breaking a glass bottle to threaten a Soc but picking up the glass after so no one gets a flat tire, that is left out of the movie and makes Ponyboy's character a little more difficult to understand.