Apple's "iPhone" announced on December 18

Since it is only local time on December 18 (Monday), will it become early morning of 19th (Tue) the next day if it is fixed to Japan time? Even so why is this true ...?

Details are as follows.
Gizmodo Knows: iPhone Will Be Announced On Monday - Gizmodo

According to this article, the iPhone is officially announced on the following Monday (December 18). Other than that it has not been revealed at all.

What kind of announcement will it be ....?