this two phrases are used to greet to people,we use "zao shang hao(早上好）"when we greet to people before 8 a.m,and use"zhong wu hao(中午好）“when we greet to people after 8 a.m but before 12 a.m

8:00-12:00 AM

zao shang hao: we alway use it when you just get up. shang wu hao: all the morning before 12:00a.m.

our chinese not often say : 【shang wu hao】 we often say【 zao shang hao 】in the moring (just like good morning ) and by the way if you write pinyin you can not show tone and our chinese can also understand what yu mean .O(∩_∩)O~

zhao shang hao is normal.