MacOS – good one hand typing Mac app

Revised because of edited question...

OmniPlan can create very nice looking Gantt charts and timelines out of project plan data. It is a full-on project planning tool, which might be overkill. But the output is quite lovely.

I recommend iStat Menus. It integrates very nicely with the mac menu bar and the Date & Time widget is very customisable and can be made to look identical to the stock Apple menubar app. You have the option to add as many time zones as you like and they are all accessible by clicking the time in the menubar (see screenshot).

iStat Menus 2 used to be free if you can find that version kicking around (needs a kernel extension tweak to work with 10.8 ML); otherwise, version 3 is a (reasonably cheap) paid app.

It also comes with a wealth of other activity monitors that can be placed on the menu bar which integrate equally nicely: both visually and functionally.