Time span of the story

Just rewatched this tonight, and in the scene after Tuptim is found after running away, the prime minister guy Kralahome says to Anna "When I warned you of this many months ago...", referring to his first meeting with Anna where he warned her about what the king is like. So I'd say the film spans less than a year.

As per Wikipedia:

In 1862, Anna accepted an offer to teach the wives and children of Mongkut, King of Siam. She served in his court until 1867, a period of nearly 6 years, first as a teacher and later as Language Secretary for the king.

In 1868, when Anna was on leave for her health in England and had been negotiating a return to the court on better terms, the king fell ill from malaria and died. The king's son, Chulalongkorn, became the new king, but did not invite Anna back to court.