Who knows when campus job fairs are usually held?

There are two relatively concentrated large-scale campus job fairs for fresh college graduates every year, one in 10- 12 and the other in March-May of the following year. At the first campus job fair, there are many so-called famous enterprises, and many enterprises will recruit the talents they need at this time. In the second campus job fair, there won't be many companies coming, most of them are local. Even famous enterprises may recruit because the number of people recruited last time is insufficient. Of course, some enterprises think that students who have had postgraduate entrance examination experience and then joined the work will have a higher knowledge reserve and will start recruiting in the following year, but less!