Chronologie et symboles de l'histoire britannique

Read the following historical context and answer the questions. The Magna Carta, signed in $1215$, established the principle that everyone, including the king, is subject to the law. If a historian calculates that the time between the signing of the Magna Carta and the English Civil War (which began in $1642$) is $X$ years, and the time between the start of the Civil War and the Glorious Revolution ($1688$) is $Y$ years, determine the total duration $T = X + Y$. Then, explain in English which symbolic shift in power this represents.