As in the topic - why do we say Obama Administration instead of Obama's?

Thanks in advance.
You can say either 'Obama's administration' or 'the Obama administration', but the latter is common because we tend to name the presidential terms and other similar time periods: The Meiji Restoration, the Kennedy years, the Hitler regime.
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PS: And welcome to English Forums, dforouzan.
Ok, thank you very much. And of course, I'm a newcomer, please forgive me for forgetting my manners.