When in time was the fair established at vanity?

William Makepeace Thackeray wrote the novel Vanity Fair in 1846 and it was published as a 19-volume monthly serial from 1847 to 1848,

The novel takes place in the early 1800s, in the first years of the Victorian era, when the country was submerging into a strong and oppressive conservative way of life.

The plot tells the saga of two families during the Napoleonic wars.