Hi. It looks like we introduced a small bug into Leash last April
which caused this build failure. (We only create a new Windows release
every few years, and our continuous integration for Windows doesn't
currently include the Leash build.)
You should be able to rectify this bug by editing
src/windows/leash/LeashView.h, searching for AddDisplayItem, and
changing the three "long" parameters (issued, valid_until, and
renew_until) to "time_t". Let me know if that works.