changeover
noun [ C usually singular ] uk/ˈtʃeɪndʒˌəʊ.vər/ us/ˈtʃeɪndʒˌoʊ.vɚ/
（体制或方法的）完全改变，大转变，更改
a complete change from one system or method to another
The changeover to the new taxation system has created a lot of problems. 彻底改用新的税收制度产生了许多问题。
Synonyms: conversiontransition