I'm not a DD, so I can't sponsor your package, but here are some thoughts.
-You need to write a manpage
-Add a watch file
-Is tz-converter really a native package?
-Add a homepage field
-Stop depending on the python-support package; use dh_python2
-Add the phrase "Initial release (closes: #754287)".
-Don't use the Ubuntu name "trusty". Continue to use Debian's "unstable"
-Fix up the spacing on line 11
-Add a version for the build-depends of debhelper (it appears that you
are using version 7, so you'd use "debhelper (>= 7)"
-You say that the license for your files is GPL-3+. Looking at the
github source, I can't find any indication that this is the case.
Perhaps you could add a notice and a copy of the license in the root
directory/as headers on your source files?
-You have not given the full text of CC-0.
-You list icons/Saki-NuoveXT-Apps-world-clock.ico as having the license
"GNU", but you do not give the text of the license.
-This is not necessary since you do not have any patches
Good luck on getting your package into Debian!