I know it's an invalid date and I'm happy in latest version it no longer hangs infinitely but your response did say report it.
So minimum reproduce case.
cron = Fugit::Cron.new("* * 31 11 *")
cron.next_time
RuntimeError: too many loops for "* * 31 11 *" #next_time, breaking, please fill an issue at https://git.io/fjJC9
from /Users/petera/.rvm/gems/ruby-2.2.10/gems/fugit-1.2.0/lib/fugit/cron.rb:225:in `block in next_time'
I know it's an invalid date and I'm happy in latest version it no longer hangs infinitely but your response did say report it.
So minimum reproduce case.