"an overlap of * days (OR weeks, etc.)" というフレーズなら、
一応はヒットするね。どういうフレーズがヒットしないって言ってるのかな？


(1) Therapy will be started as soon as possible once your heart beat is controlled.
★An overlap of up to 2 days★ with the injection may occur.
（医学ニュースのサイト）
https://www.news-medical.net/drugs/Cordarone-X.aspx

(2) It is critical for the continuity of the data stream to have both instruments ●overlap●
to allow for syncing the measurements, allowing the new more accurate TCTE calibration
to be transferred to SORCE TIM, and then to earlier ◆overlapping measurements◆,
so greatly increasing the accuracy and value of the overall TSI record.
Mission scientists hope for ★an overlap period of about ten days★ for the two instruments in space.
（宇宙開発についてのニュースサイト）
https://phys.org/news/2013-12-instrument-sun-effects-earth.html