switchover
noun [ C ] uk/ˈswɪtʃˌəʊ.vər/ us/ˈswɪtʃˌoʊ.vɚ/
转换，转变;彻底改变
a change from using or doing one thing to another
The switchover to daylight saving time represents a one percent saving of electricity annually. 使用夏时制后，每年的电力使用量节省了百分之一。