Engels and Marx.
Few years have the lasting significance of 1844 because that is the year that the two thinkers met and started developing/preaching their ideas about governance and socialization. It also happens to be the year that ended the 2300 year prophecy and for told of the return of Jesus Christ. That second part presumably didn’t take place but did harken a new age of religions such as Seventh Day adventists and the followers of Bahá’í.
While some religions, such as seventh day, flourished under the rule of their founding member , others came to be relegated to back pages and side streets.
Change happens on a lot of fronts. You cannot become acquainted with one without considering the others. 1844 was about change on multiple fronts.