Whose Birthday?

My aunt loves birthdays. She just can't remember them.

“Your birthday is in January,” she says. No, in February.

“Your sister, she is April.” No, July.

“Your dad? August!” No, September.

“Your mum is in October.” No, November.

“And the baby is in December,” she says. Yes! Right at last!

Then she smiles. “So… whose birthday is in December?”