South Africans are preparing to celebrate the 95th birthday of Nelson Mandela on Thursday, even as the former president remains critically ill in a hospital.

The Nelson Mandela Center of Memory and other groups have asked people to volunteer 67 minutes to charity in honor of what they say are the 67 years that Mandela served his community. The United Nations has also recognized the anti-apartheid leader's birthday as an opportunity to honor his legacy, and activities are planned around the globe.

President Jacob Zuma will mark the occasion by overseeing the donation of houses to poor families in the Pretoria area.

Mandela was admitted to a Pretoria hospital on June 8 for a recurring lung infection.