[bemmu]

Btw. is there some way to ask google "when it is 10am in new york, what time is it in tokyo?".

[truebosko]

It'll just bring back some results that may be useful. However, Wolfram Alpha does this pretty well..

http://www.wolframalpha.com/input/?i=when+it+is+10am+in+new+...

It doesn't understand the question exactly, but still shows the current times, and quick math could tell you what it would be at 10am. Some playing with the query and adding "timezone" into it gets you closer to the actual answer you're asking though