When did women stop dressing modest?

There are still many women who dress modest.

It all depends on your definition of modest, it could be as early as the 1900s, even earlier if you're a stickler old woman. It could be around 1960 when skirts got short and boots got high, the 1970s when bellies started peeking out, 1980s when fashion went crazy with styles and colors, 1990s when all of the above was a 'problem'.