What's the difference between the calendars in the south and the north?

Roughly the same. There are also differences.

The calendar in the north has the prompt of "counting nine". The calendar in the south has a hint of "entering the plum blossom".

Twenty-four solar terms are most suitable for the Central Plains, South China and Northeast China, but not suitable.

"Rivers open in July and September, and swallows come in August and September." Heilongjiang is still a world of ice and snow in July and September, and the ice on the river is one meter thick!