This week's portion Va'era, includes the infliction of the first seven plagues upon Pharaoh and the Egyptians. In reading the few verses of this story, time seems to be fleeting. After seven days of the red Nile, frogs cover the land.
All indications point to a rapid succession of various diseases and afflictions.
Tradition, however, suggests that it was one year, enough time to accommodate the shift in both Pharaoh's and the Egyptians' opinion regarding the release of the Israelites. Even though Pharaoh feared being overpowered by the enormous numbers of Israelites, the society benefited from the vast labor force of these slaves. The labor was cheap and handled all of the most menial tasks. Relinquishing a significant sector of the societal infrastructure required serious re-thinking on Pharaoh's part, and by his countrymen. It takes time to not only make the physical and infrastructure alterations, but it means that it requires a change in the psychological state as well.