Japan was never colonised by Europeans
In the context of disorders involving emotion and mood, it can be inferred that Dr. Henderson is likely to diagnose Cathy with major depressive order. The symptoms of these are shown on Cathy wherein she is unhappy and feels worthless most of the time, she does not eat or sleep well and has even contemplated suicide and has been experiencing these distressing symptoms for almost 3 weeks.
I think you're looking for the name for this event? This is eclipse, and more specifically solar eclipse: when the Sun cannot be seen because it is covered by the moon between the Sun and Earth
