When Sawda bint Zama grew old, she gave her day to Ayesha. So the Messenger of Allah ﷺ used to allot to Ayesha both her own day and Sawda's.
لما كبرت سودة بنت زمعة، وهبت يومها لعائشة. فكان رسول الله ﷺ يقسم لها بيوم سودة.
Bukhari narrated it in the Book of Marriage (5212), and Muslim in the Book of Breastfeeding (1463), both from the hadith of Hisham bin Urwa, from his father, from Ayesha, who said, and she mentioned it.