Sestercentennial
The word for the 250th anniversary of an organization is "semiseptcentennial." This term combines "semi-" meaning half and "septcentennial" referring to a 700th anniversary, but in this context, it is often used to denote significant milestones such as a 250th celebration. Alternatively, it can also be referred to as a "225th anniversary" celebration, though the specific term for 250 years is less commonly used.
In 2009.
Semiquincentennial
September 7
What Not to Wear - 2003 250th Anniversary Episode was released on: USA: 29 January 2010
Pearl.
November 2009
centenary
2026
2/250 = 0.8%
No
One common definition is quarter-millennialThe MOST correct answer is Sestercentennial literally meaning half way between 200 and 300 years.