Ambiguous time when parsing dates with daylight savings using Chronic

[stanhu]

Here's a test that reproduces the problem:

diff --git a/spec/module_spec.rb b/spec/module_spec.rb
index a0c980e..893212f 100644
--- a/spec/module_spec.rb
+++ b/spec/module_spec.rb
@@ -288,6 +288,15 @@ describe EtOrbi do
         expect(t.strftime('%Y-%m-%d')).to eq(t1.strftime('%Y-%m-%d'))
         expect(t.strftime('%H:%M:%S')).to eq('12:00:00')
       end
+
+      it 'handles days that have ambiguous daylight savings conversions' do
+
+        Time.active_support_zone = 'America/Chicago'
+
+        t = EtOrbi.parse('2020-11-01 00:00:00')
+
+        expect(t.class).to eq(EtOrbi::EoTime)
+      end
     end
   end

It fails with:

Failures:

  1) EtOrbi.parse when Chronic is defined handles ambiguous daylight savings conversions
     Failure/Error: secs = zone.local_to_utc(local).to_f

     TZInfo::AmbiguousTime:
       Time: 2020-11-01 01:00:00 UTC is an ambiguous local time.
     # ./lib/et-orbi/make.rb:42:in `parse'
     # ./spec/module_spec.rb:296:in `block (4 levels) in <top (required)>'

I described the problem in-depth in https://gitlab.com/gitlab-org/gitlab/issues/37014#note_248974118.

Essentially, when Chronic is used, the time is advanced unnecessarily:

t = Chronic.parse('2020-11-01 00:00:00')
=> 2020-11-01 01:00:00 -0500
str = [ t.strftime('%F %T'), nil ].compact.join(' ')     
=> "2020-11-01 01:00:00"
zone = TZInfo::Timezone.new("America/Chicago")
=> #<TZInfo::DataTimezone: America/Chicago>
zone.local_to_utc(t)
Traceback (most recent call last):
        9: from /opt/gitlab/embedded/bin/irb:23:in `<main>'
        8: from /opt/gitlab/embedded/bin/irb:23:in `load'
        7: from /opt/gitlab/embedded/lib/ruby/gems/2.6.0/gems/irb-1.0.0/exe/irb:11:in `<top (required)>'
        6: from (irb):35
        5: from (irb):35:in `rescue in irb_binding'
        4: from /opt/gitlab/embedded/lib/ruby/gems/2.6.0/gems/tzinfo-1.2.5/lib/tzinfo/timezone.rb:464:in `local_to_utc'
        3: from /opt/gitlab/embedded/lib/ruby/gems/2.6.0/gems/tzinfo-1.2.5/lib/tzinfo/time_or_datetime.rb:324:in `wrap'
        2: from /opt/gitlab/embedded/lib/ruby/gems/2.6.0/gems/tzinfo-1.2.5/lib/tzinfo/timezone.rb:468:in `block in local_to_utc'
        1: from /opt/gitlab/embedded/lib/ruby/gems/2.6.0/gems/tzinfo-1.2.5/lib/tzinfo/timezone.rb:409:in `period_for_local'
TZInfo::AmbiguousTime (Time: 2020-11-01 01:00:00 UTC is an ambiguous local time.)

I propose two ways to solve this here:

1. An option to disable the use of Chronic
2. Fix the time zone handling when Chronic is in use

Chronic is probably causing issues because it doesn't handle Daylight Savings well: mojombo/chronic#147

[jmettraux]

@stanhu thanks for the patch, as you've seen, it's merged. I will dig a bit deeper tomorrow morning (HK time).

I will try to reproduce your root issue, since

  Time.active_support_zone = 'America/Chicago'          
  t = EtOrbi.parse('2020-11-01 00:00:00')  

is not making any problem on my system. I'll think about how to trigger that here.

I also have to look at the CI appveyor :-(

When I have something decent, I will release.

Thanks so far.

[stanhu]

@jmettraux Thanks! Did you remember to require 'chronic' first? Have you tried changing the spec that was merged to enable_chronic: false? That fails for me.

[stanhu]

Hmm, we might want to revert #24 since the extra opts are leaking into Chronic options. Besides, I think the real issue is mojombo/chronic#147 (comment).

[jmettraux]

Did you remember to require 'chronic' first?

Yes,

et-orbi/spec/module_spec.rb

Lines 241 to 243 in 8425ca5

	before :each do
	require_chronic
	end

[stanhu]

It's possible the time zone on your system also matters.

[stanhu]

I've submitted mojombo/chronic#396 to fix this problem.

[jmettraux]

@stanhu wrote:

It's possible the time zone on your system also matters.

May I know what Ruby version, what OS, and what timezone combination exhibits the problem for you?

Thanks in advance.

[jmettraux]

@stanhu wrote:

Have you tried changing the spec that was merged to enable_chronic: false? That fails for me.

Yes, I first worked with your spec, but it didn't fail for me, Chronic or no-Chronic. Sorry, I had to change it to reflect the true purpose of enable_chronic: false, turning off Chronic as a middle-man.

[stanhu]

On Linux, it looks like setting the system clock via timedatectl makes the EtOrbi.parse('2020-11-01 00:00:00', enable_chronic: true) test fail:

timedatectl set-timezone "America/Chicago"

[jmettraux]

@stanhu What Linux flavour, what Ruby version, what Chronic version? Thanks in advance.

[stanhu]

@jmettraux I've been using Ubuntu 18.04, Ruby 2.6.3, and Chronic v0.10.2.

[jmettraux]

Thanks for all the investigation work and the contributions. Since it's Chronic issue, I am closing this one.