From d780d325aca383a6a8b010a6622bddbc09652da5 Mon Sep 17 00:00:00 2001
From: Oliver Ford <oford@gocardless.com>
Date: Mon, 2 Nov 2026 15:48:05 +0000
Subject: [PATCH 1/2] Roll `TimeWithZone`s forward in DST-aware manner

Presently, `roll_forward`, `next_business_day`, et al. use
`day_interval_for`'s definition of `1` (days) for `Date` objects, or
`60 * 60 * 24` (seconds) otherwise.

Falling into the latter category, `ActiveSupport::TimeWithZone` objects
in Rails environments have their date component adjusted in a manner
which is not timezone-aware, and thus corrupts the time component when
the change spans a DST transition. For example:

    t = TimeWithZone.new(Time.new(2026,10,23,12,0,0), ActiveSupport::TimeZone::country_zones(:gb)[0])

constructs `t` as noon UTC in `Europe/London` while BST is active, i.e.
`t` is 1pm local time.

    next_business_day(t)

gives `2026-10-26 12:00:00.000000000 GMT +00:00`, that is, still noon
UTC, but now also noon local time, as the next business day was post
transition to GMT.

This commit addresses the issue by detecting `TimeWithZone`s, and using
ActiveSupport's `Integer#day` as for the interval in such cases; in the
above example giving `2026-10-26 13:00:00.000000000 GMT +00:00` as
expected.
---
 lib/business/calendar.rb       |  8 +++++++-
 spec/business/calendar_spec.rb | 14 ++++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/lib/business/calendar.rb b/lib/business/calendar.rb
index 3fbae69..fc21f23 100644
--- a/lib/business/calendar.rb
+++ b/lib/business/calendar.rb
@@ -209,7 +209,13 @@ def business_days_between(date1, date2)
     end
 
     def day_interval_for(date)
-      date.is_a?(Date) ? 1 : 3600 * 24
+      if date.is_a?(Date)
+        1
+      elsif defined?(ActiveSupport::TimeWithZone) && date.is_a?(ActiveSupport::TimeWithZone)
+        1.day
+      else
+        3600 * 24
+      end
     end
 
     # Internal method for assigning working days from a calendar config.
diff --git a/spec/business/calendar_spec.rb b/spec/business/calendar_spec.rb
index 9ee37aa..26050d1 100644
--- a/spec/business/calendar_spec.rb
+++ b/spec/business/calendar_spec.rb
@@ -1049,4 +1049,18 @@
 
     it_behaves_like "common"
   end
+
+  context "(using TimeWithZone objects)" do
+    before do
+      stub_const("ActiveSupport::TimeWithZone", Class.new(Time))
+      Integer.define_method(:day) { self * 60 * 60 * 24 }
+    end
+
+    after { Integer.remove_method(:day) }
+
+    let(:date_class) { ActiveSupport::TimeWithZone }
+    let(:day_interval) { 1.day }
+
+    it_behaves_like "common"
+  end
 end

From 10ade9d356a49efc17822950f748592b272c89dc Mon Sep 17 00:00:00 2001
From: Oliver Ford <oford@gocardless.com>
Date: Tue, 3 Nov 2026 12:27:52 +0000
Subject: [PATCH 2/2] Bump to v3.2.0

---
 CHANGELOG.md            | 4 ++++
 lib/business/version.rb | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index aa7385e..0b0ac6b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 ## Upcoming
 
+## 3.2.0 - Nov 3, 2026
+
+- Advance `ActiveSupport::TimeWithZone`s whole days across DST boundaries #339
+
 ## 3.1.0 - Sept 28, 2026
 
 - Fix `business_days_between` not counting extra working dates in full weeks #34 - thanks @anatoliliotych!
diff --git a/lib/business/version.rb b/lib/business/version.rb
index 09ba1f3..097d139 100644
--- a/lib/business/version.rb
+++ b/lib/business/version.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module Business
-  VERSION = "3.1.0"
+  VERSION = "3.2.0"
 end