What changes did Jonas have to make to the plan and how did these changed make the escape harder?

In spite of the plan to leave in two weeks, Jonas is forced to leave shortly after dark that night, although he has to dodge work crews and has no time to go to the Annex. He leaves without regret on his bicycle, although he feels sad at leaving The Giver without saying goodbye. The reason for the rush is that at today's evening meal, his father said that when they tried having Gabriel stay overnight at the Nurturing Center, he cried all night, so even Father had to vote for his release. Horrified, Jonas then learned that Gabriel would be released in a hurry tomorrow morning, since Naming Ceremony preparations are looming. He is therefore absconding with Gabriel.