Due to historical reasons, it is not rare that related languages become arbitrarily distant and different (including distribution of topics) for a period of time, only to become closer for another period of time. Traditionally, the degree of topic similarity was assets by sociolinguistics on the basis of their expertise starting with of the effect of many aspects governed by some set of rules governing the Society. However, it is hardly possible to cover a large amount of data only by human effort. We present a methodology of diachronic investigation on newspapers articles which determines the significant changes in the distribution of topics that best reflects the difference between historical regional interests.