Phrases like "of a afternoon" bring to mind a specific setting ... early summer, in the garden, seated around an umbrella table, soft breeze, sandwiches with the crusts cut off, gentle conversation.
In that setting, "I love lazing around with friends of a summer afternoon" seems appropriate.

But change the setting and phrases like that seem out of place, old fashioned, archaic even.
How often do we change our words, and the selection of them, according to where we are and who we are with?
wow