Christians celebrate the unity octave from 18 – 25 January. Traditionally January 18 has been the Feast of the Chair of St. Peter and January 25 is the Feast of the conversion of St. Paul.
This is very symbolic – authority to conversion.
2000 years ago Jewish Saul had a conversion experience on his way to Damascus when he went to persecute the "Followers of the Way".
What was this conversion? – Before his conversion, he was an ethnocentric person and had xenophobia. This conversion made him understand “unity in diversity” & also “diversity in unity”.
Unity is not possible until and unless we have this conversion!