How did the people told what year it was for Christ?

They didn’t.For them it was just a year as 2019 is a year. Remember that outside of Judea and Samaria none of Christ had heard. The “before and after Christ” was introduced only later, after the introduction of Christianity in Europe. Before that, it was just like in every linear era. Re: Chinese and Jewish census.

Copied directly from ‘ Year count ‘ in Wikipedia census-Wikipedia, come on say, just about every civilization has its own annual census–Moreover, it was often still used “the umpteenth year of King Zusofzo”

The Christian era has become commonplace in the whole world after the Middle ages through the European expansion of praying, although certain peoples or religions also have their own annual census in addition to the Christian era:

• Masonic Census, from 4000 BC
• Jewish Year Count, from 3761 BC, with nowadays years of average 365 170177/689472 = 365.2468 days
• Chinese Census, from 2697 BC
• Buddhist era, from 543 BC
• Thai Year count, from 543 BC
• Seleucid era, from 312 BC
• Ethiopian year Count, from 8 A.D.
• Diocletisian era, from 284 A.D.
• Islamic Year count, from 622 N. Chr., with years of approximately 354 days
• Japaneseera, from every throne ascent of the Emperor: from 1989 A.D.

Under Emperor Akihito; From 2019 N. Chr.Under Emperor Naruhito;

No longer in use

• Egyptian king lists from approximately 3000 v. Chr.

Up to the beginning of the Christian year count, see also Egyptian chronology

Traditionally, a new annual census was initiated with each accession.In the Bible, one often reads a text like “in the eighteenth reign of King Jerobeam”