diff --git a/Makefile b/Makefile
index 86f94f54..09cbf1b7 100644
--- a/Makefile
+++ b/Makefile
@@ -15,6 +15,7 @@ install: deps
 	@# `make install` installs the editable version of OpenFisca-France.
 	@# This allows contributors to test as they code.
 	pip install -e '.[dev]' --upgrade --use-deprecated=legacy-resolver
+	pip install --editable git+https://github.com/openfisca/openfisca-core.git@add-weeks#egg=OpenFisca-Core[web-api]  # use a specific branch of OpenFisca-Core
 
 build: clean deps
 	@# Install OpenFisca-Extension-Template for deployment and publishing.
diff --git a/openfisca_country_template/tests/situations/parenting_allowance.yaml b/openfisca_country_template/tests/situations/parenting_allowance.yaml
index bce6d594..d0ffe448 100644
--- a/openfisca_country_template/tests/situations/parenting_allowance.yaml
+++ b/openfisca_country_template/tests/situations/parenting_allowance.yaml
@@ -2,8 +2,8 @@
 # We can run this test on our command line using `openfisca-run-test tests/situations/income_tax.yaml`
 
 - name: Parenting allowance for a two parent household with little income
-  description: Parenting allowance relies on the incomes on the parents and ages of the children
-  period: 2020-01
+  description: Parenting allowance relies on the fortnight incomes of the parents and ages of the children
+  period: 2022
   absolute_error_margin: 0
   input:
     household:
@@ -12,14 +12,14 @@
     persons:
       Phil:
         birth: 1981-01-15
-        salary:
-          2017-01: 250
-          2018-01: 250
+        weekly_salary:
+          week:2022-W01:2: 250
+          week:2022-W03:2: 250
       Saz:
         birth: 1982-01-15
-        salary:
-          2017-01: 250
-          2018-01: 251
+        weekly_salary:
+          week:2022-W01:2: 250
+          week:2022-W03:2: 251
       Caz:
         birth: 2010-01-15
       Eille:
@@ -29,5 +29,5 @@
   output:
     household:
       parenting_allowance:
-        2017-01: 600
-        2018-01: 0
+        2022-W03: 600
+        2022-W05: 0
diff --git a/openfisca_country_template/variables/benefits.py b/openfisca_country_template/variables/benefits.py
index 3703113d..56525665 100644
--- a/openfisca_country_template/variables/benefits.py
+++ b/openfisca_country_template/variables/benefits.py
@@ -7,7 +7,7 @@
 """
 
 # Import from openfisca-core the Python objects used to code the legislation in OpenFisca
-from openfisca_core.periods import MONTH
+from openfisca_core.periods import MONTH, WEEK
 from openfisca_core.variables import Variable
 
 # Import the Entities specifically defined for this tax and benefit system
@@ -91,14 +91,13 @@ def formula(person, period, parameters):
 class parenting_allowance(Variable):
     value_type = float
     entity = Household
-    definition_period = MONTH
+    definition_period = WEEK
     label = "Allowance for low income people with children to care for."
     documentation = "Loosely based on the Australian parenting pension."
     reference = "https://www.servicesaustralia.gov.au/individuals/services/centrelink/parenting-payment/who-can-get-it"
 
     def formula(household, period, parameters):
-        """
-        Parenting allowance for households.
+        """Parenting allowance for households.
 
         A person's parenting allowance depends on how many dependents they have,
         how much they, and their partner, earn
@@ -107,12 +106,12 @@ def formula(household, period, parameters):
         """
         parenting_allowance = parameters(period).benefits.parenting_allowance
 
-        household_income = household("household_income", period)
+        household_income = household("household_weekly_income", period.last_2_weeks, options = ["add"])
         income_threshold = parenting_allowance.income_threshold
         income_condition = household_income <= income_threshold
 
         is_single = household.nb_persons(Household.PARENT) == 1
-        ages = household.members("age", period)
+        ages = household.members("age", period.first_month)
         under_8 = household.any(ages < 8)
         under_6 = household.any(ages < 6)
 
@@ -132,3 +131,15 @@ def formula(household, period, _parameters):
         """A household's income."""
         salaries = household.members("salary", period)
         return household.sum(salaries)
+
+
+class household_weekly_income(Variable):
+    value_type = float
+    entity = Household
+    definition_period = WEEK
+    label = "The sum of the salaries of those living in a household"
+
+    def formula(household, period, _parameters):
+        """A household's income."""
+        salaries = household.members("weekly_salary", period)
+        return household.sum(salaries)
diff --git a/openfisca_country_template/variables/income.py b/openfisca_country_template/variables/income.py
index 1b48144c..899c56ec 100644
--- a/openfisca_country_template/variables/income.py
+++ b/openfisca_country_template/variables/income.py
@@ -8,7 +8,7 @@
 
 # Import from openfisca-core the Python objects used to code the legislation in OpenFisca
 from openfisca_core.holders import set_input_divide_by_period
-from openfisca_core.periods import MONTH
+from openfisca_core.periods import MONTH, WEEK
 from openfisca_core.variables import Variable
 
 # Import the Entities specifically defined for this tax and benefit system
@@ -25,6 +25,16 @@ class salary(Variable):
     reference = "https://law.gov.example/salary"  # Always use the most official source
 
 
+# This variable is also a pure input, but with a different definition period
+class weekly_salary(Variable):
+    value_type = float
+    entity = Person
+    definition_period = WEEK
+    set_input = set_input_divide_by_period  # Optional attribute. Allows user to declare a salary for a week. OpenFisca will then multiply the weekly amount over the weeks requested.
+    label = "Weekly Salary"
+    reference = "https://law.another-gov.example/salary"  # Always use the most official source (and https)
+
+
 class disposable_income(Variable):
     value_type = float
     entity = Person