"Sunday Morning." A pretty straightforward title, right? But, it provides information about the setting that we otherwise wouldn’t know from reading the poem. If you hadn’t read the title, you’d probably wonder why in the world this woman keeps thinking about the sacrifice of Jesus. Some scholars even believe that the poem is set on Easter Sunday, which celebrates the resurrection of Christ after his crucifixion. This is quite possible – it does seem like the poem takes place in the springtime – but, even if the poem is set at Easter, Stevens doesn’t want us to know that. He wants to keep the title general. This could be any warm Sunday morning.
Although the poem gives us the very specific thoughts of one woman, Stevens figures that most Americans can probably relate to the experience of enjoying a late breakfast in their pajamas on the "day of rest," when things slow down and people have time to think serious thoughts. Also, keep in mind that "Sunday" also reads as "Sun-day," the day of the sun. We normally associate Sunday with the Christian calendar, but, here, it could refer to a different kind of "day of worship": worship of the sun.