CLDC-3463: Fix bug with vacdays calculation

app/models/derived_variables/lettings_log_variables.rb

@@ -306,9 +306,9 @@ private
     return unless startdate
 
     if mrcdate.present?
-      (startdate - mrcdate).to_i / 1.day
+      startdate.to_date - mrcdate.to_date
     elsif voiddate.present?
-      (startdate - voiddate).to_i / 1.day
+      startdate.to_date - voiddate.to_date
     end
   end
 

lib/tasks/recalculate_vacdays.rake

@@ -0,0 +1,5 @@
+desc "Recalculate vacdays after bugfix for daylight savings time changes"
+task recalculate_vacdays: :environment do
+  logs = LettingsLog.filter_by_years(%w[2023 2024]).where.not(vacdays: nil)
+  logs.each(&:save!)
+end

spec/models/lettings_log_spec.rb

@@ -1514,6 +1514,24 @@ RSpec.describe LettingsLog do
       expect(record_from_db["has_benefits"]).to eq(1)
     end
 
+    describe "deriving vacant days" do
+      it "correctly derives vacdays from startdate and mrcdate across DST boundaries" do
+        log = build(:lettings_log, startdate: Time.zone.local(2024, 4, 1), mrcdate: Time.zone.local(2024, 3, 30))
+
+        log.set_derived_fields!
+
+        expect(log.vacdays).to be 2
+      end
+
+      it "correctly derives vacdays from startdate and voiddate across DST boundaries" do
+        log = build(:lettings_log, startdate: Time.zone.local(2024, 4, 1), mrcdate: nil, voiddate: Time.zone.local(2024, 3, 30))
+
+        log.set_derived_fields!
+
+        expect(log.vacdays).to be 2
+      end
+    end
+
     context "when updating values that derive vacdays" do
       let(:lettings_log) { create(:lettings_log, startdate:) }