If you examine the styles that came before the Regency era, you will discover that a significant shift occurred quickly, roughly between the very early 1800s
Fashion 1816 — Blog — Ann Lethbridge
Regency Fashion History 1800-1825 Beautiful Pictures Empire Line Dresses
The Late Georgian/Empire/Regency Era 1790-1820 – Maggie May Clothing- Fine Historical Fashion
Fashion Revolution During the Regency Period – Fashion Gone Rogue
1795–1820 in Western fashion - Wikipedia
Bridgerton Inspired Clothing Brands To Try Sydne Style, 42% OFF
What prompted the dramatic change in women's fashion between the Regency era and the Victorian era? I.e. why did fashion become so much more restrictive? - Quora
Dress History Corner — Pride And Prejudice 2005 - Costume Analysis
Exploring the Elegant Revival of Regency Era Fashion
Regency Era Fashion History, Culture And Lifestyle