noun
transition period; cutover period
Used in computing and project contexts for the period during which a system, process, or state is being changed over.
新しいシステムへの移行期には、トラブルが起こりやすい。
During the transition period to the new system, problems are likely to occur.
移行期の計画をしっかり立てる必要がある。
We need to make a solid plan for the transition period.
過渡期 also means 'transition period', but is more general and often used for societal or historical transitions, whereas 移行期 is common in technical and business contexts.
Compound of 移行 (transition) + 期 (period).