Worrying

As I was walking up the road this morning I realised that I have spent 30 years worrying about a lyric by Curved Air, the prog rock band I loved when I was in the Sixth Form.
'On a bright summer's day
In the middle of May...'
sings Sonja Kristina.
But May's not in the summer! It's in the spring! Or have they moved summer and I didn't notice? This has confused me for years and years, until this morning when it finally dawned on me that they were just rhyming May with day, and not shifting the seasons about after all.