fugit: Endless loop after call Fugit::Cron#next_time with time zone 'CST'

environment:

• ruby 2.3.3p222
• fugit 1.1.6
• Time.now.zone is CST(+08:00)

code:

Time.now.utc # "2019-01-02T05:25:53.960Z"
cron = Fugit.do_parse_cron('0 0 1 1 *')
cron.next_time.to_s

expected:

"2019-12-01 00:00:00 +0000"

got:

Endless loop

What I found:

After some debugging, I thought the method TimeCursor#inc_mont doesn’t work right in timezone CST (maybe all positive east of UTC timezones).

https://github.com/floraison/fugit/blob/6488c5f4e47ac63a2a5b7f290656a344ff9d2ca9/lib/fugit/cron.rb#L88 This line will parse the year and month as time zone CST, and then transfer to UTC.

For example:

::EtOrbi.make(2019, 2).to_s

expected: 2019-02-01 00:00:00 +0000 but got: 2019-01-31 16:00:00 +0000

The month isn’t increased, and the loop in next_time will last forever.

Thank you for your work.