You use today to refer to this day on which you are speaking or writing.
How are you feeling today?
你今天感觉怎么样?
You can refer to the present period of history as today.
The United States is in a serious recession today.
如今,美国正处于严重的萧条时期。
You use today to refer to this day on which you are speaking or writing.
Today is Friday, September 14th.
今天是9月14日,星期五。
You can refer to the present period of history as today.
In today's America, health care is one of the very biggest businesses.
在当今的美国,医疗保健是最大的行业之一。