The music and lyric for Good Day Sunshine were both influenced by The Lovin' Spoonful's hit Daydream, which in turn was influenced by the style of the Supremes' Baby Love. Paul wrote the tune "on a particularly sunny day."
"It was really very much a nod to The Lovin’ Spoonful’s Daydream, the same traditional, almost trad-jazz feel. That was our favourite record of theirs. Good Day Sunshine was me trying to write something similar to Daydream. John and I wrote it together at Kenwood, but it was basically mine, and he helped me with it." - Paul