Why this header of "世界日报" is written as "世界曰报"？ See the picture. 

There is an obvious mistake: the third character is written as "曰" (yue) instead of "日" (ri). Why it is not written correctly as "日" such as the following?
It's correctly written, but in a different font called 隶书 Clerical script. It's one of the archaic style of writing. In general Chinese characters in 隶书 look wider, which makes 日 looks like 曰 in regular fonts.