Tokyo Jidai (Tokyo Period) (東京時代)
The Tokyo period is a notion devised as a way to refer to the period after 1868, when the Edo bakufu collapsed and the Meiji restoration was started, within the framework of periodization of Japanese history.
Today, the history after the Meiji restoration is generally periodized with the use of gengo (name for an emperor's period of reign), such as the Meiji period, Taisho period, Showa period and Heisei period, but the history before the Meiji restoration is normally periodized with the use of names of political centers, such as the Kamakura period and Edo period (except for the periods for which the political center cannot be ascertained, such as the Yayoi period and Sengoku period); thus there comes up a view that calling the periods after the Meiji restoration with their gengo is inappropriate. From that viewpoint, the period of time after the Meiji restoration should be collectively referred to as the "Tokyo period" because the political center has existed in Tokyo since the restoration.
However, the term "Tokyo period" is not used in general, except in some books that use the term to refer to modern or contemporary Japan, probably because there is a big difference in political systems between Japan under the Constitution of the Empire of Japan and Japan under the present Constitution of Japan, and because it may seem unnatural to call a period that stretches beyond 100 years with the same name.
And the periodization is a method to distinguish the present day from the past. However, it cannot be denied that the present framework of periodization may change in the future according to changing times. For example, if the capital is relocated from Tokyo or if Tokyo is renamed, the term "Tokyo period" may be used for collectively referring to the period since the Meiji era in order to distinguish the times before and after such relocation or rename.