The International Day of Charity was established with the objective of sensitizing and mobilizing people, NGOs, and stakeholders all around the world to help others through volunteer and philanthropic activities.

The date of 5 September was chosen in order to commemorate the anniversary of the passing away of Mother Teresa of Calcutta, who received the Nobel Peace Prize in 1979 “for work undertaken in the struggle to overcome poverty and distress, which also constitute a threat to peace.”

Here is the link for more information https://www.un.org/en/observances/charity-day