I’ve found this to be a pretty useful site for all my calculations with dates.
If I want to know, for example, how many days it has been since I got married or when our 10000 days anniversary is :), I use this site. Or how many days/months ago some event took place. And so on.
However, to find out current time somewhere in another part of the world, one can simply google ‘current time X‘ – and it’ll be there. 🙂