Among these periods of English Literature which Period’s inception is the oldest?

The Latest Period of English Literature is the Post-Modern period (1939-present).
Before this period, The Modern English period was one of the most significant literary periods.
The Modern Period (1901-1939) is divided into two shorter periods.
One is The Edwardian Period (1901-1910)
and the other is The Georgian Period (1910-1939).
Source: An ABC of English Literature, Dr. M Mofizar Rahman.