It has been a great day. 和 It was a great day. 的差別在哪裡？如果不好說明，請提供一些例句。

"It has been a great day" = "until now", the day is still continuing.

"It was a great day" = the day is finished.

In the evening you can talk about today using either one.

To talk about another day in the past, you must use "was".

To talk about today in the morning or afternoon, you must use "has been".