Sentence with infinitive form verb

Question

I'm reading an article which starts with the sentence:

Началом русского авангарда принято считать 1907 год...

I understand that началом русского авангарда is the object of считать, so why is считать in the infinitive form here?

Answer 1

Принято считать — is a predicate of an impersonal sentence when the subject is missing. The same construction in English usually has an impersonal "it" as a formal subject. Some more examples

Нужно сказать, трудно поверить, интересно отметить, надо признать,хочется верить etc.

The infinitive in these predicates comes after a verb or an adverb (слова состояния)

Answer 2

Because it is part of 'принято // считать' which may be translated as 'it is customary // to regard'.