[roddyp]

Hmm,

I don't understand it -  I'm using two computers with Windows 10, one is 32 bit, IDE 1.8.0, the second is 64 bit with IDE 1.7.10. And I use Time library from
.rar package without any problems ...

In this case, I would try to uninstall the entire IDE, delete the old directories and do a completely new installation. Sorry, otherwise, unfortunately I can not advise.

I don't understand it either   I've tried fresh install of Arduino and all libraries, and every time the same result. Windows 10, x64. I'll have to try it on a different PC next.

I guess the first question to ask is : Do you have a file called "time.h" here? C:\Program Files (x86)\Arduino\hardware\tools\avr\avr\include
(This is part of the avr platform library rather than the "Time" library, and I think gets installed as part of ther Arduino setup)

The second question is what version of Time library does Arduino think you have installed? (from Sketch/Include Library/Library Manager)

I'll put that on hold for now!