Check the time in another country when planning a phone call, online meeting, or chat. These sites typically carry a lot of advertising. Sorry, that's the business model, but the sites are useful.

Everytimezone  - an interactive graphical interface to compare your time across time zones.

The Time Now  - plan meetings across multiple time zones, and more.

The World Clock  - comprehensive with many options.

Time Zone Map - world time zones, dates, and times.

World Clock Meeting Planner  - find the best time for an online conference across time zones.

Time and Date - all the above features, including a very useful Date Calculator, which can show the date for a given number of days, years, etc after or before a given date.

Alternatively, watch the stars and planets and use their position to navigate in time and space. See the Stellarium