Installing gnotime (emerge gnotime) gave me the following error:
Perhaps you should add the directory containing `libgtkhtml-2.0.pc'
to the PKG_CONFIG_PATH environment variable
No package 'libgtkhtml-2.0' found
configure: error: Library requirements (libgtkhtml-2.0 >= 2.0.0) not met; consider adjusting the PKG_CONFIG_PATH environment variable if your libraries are in a nonstandard prefix so pkg-config can find them.
!!! ERROR: app-office/gnotime-2.1.6 failed.
!!! Function econf, Line 338, Exitcode 1
!!! econf failed
I had to manually install the library:
emerge gnome-extra/libgtkhtml/libgtkhtml-2.4.0.ebuild
to get it working