These changes often occur quickly, over a period of weeks.

An increase of 6 percent occurred over the same period for private schools.

His return occurred over three months until March 26, 2009.

But we'll have to see what occurs over the next couple weeks.

Watch for changes that occur over a period of weeks to a month.

The change would occur over a 24-year period starting in 2003.

Similar events occurred at 8am local time, August 1, all over the world.

The actual move occurred over the period from 1827 to 1836.

A second race occurred ten weeks later over the same distance.

A more moderate increase of 6 percent occurred over the same period for private schools.