The official WAM news agency published pictures showing Sheikh Khalifa meeting a number of prominent officials and rulers of the other six emirates that with Abu Dhabi form the UAE.
The guests came to his Abu Dhabi palace on the first day of the Eid, which marks the end of the fasting month of Ramadan, and Sheikh Khalifa appeared to be in good spirits, according to the pictures and a short video posted on WAM's Twitter account.
The president is also the ruler of the oil-rich emirate of Abu Dhabi, the wealthiest of the seven emirates that form the UAE as it sits on the bulk of the nation's oil wealth.
After his illness, Sheikh Khalifa's half-brother Crown Prince Sheikh Mohammed bin Zayed took over as de facto ruler, though Sheikh Khalifa continued to issue decrees and deal with protocol issues.
In addition to Abu Dhabi, the UAE comprises the emirates of Ajman, Dubai, Fujairah, Ras al-Khaimah, Sharjah and Umm al-Qaiwain.