Q. How much time elapsed between the first plague in Exodus and the last (passover)?
A. While the Bible doesn’t specify the duration of time required for the 10 plagues to run their course, scholars have estimated that it took several months, perhaps as many as nine. They base this on various things, the flood stages of the Nile, the growing season, etc. Knowing that the 10th plague was memorialized by the Passover, which takes place in March/April, they then backed into an estimated start date using these factors as their guide.