diff --git a/.gitignore b/.gitignore
index 495bb5e..2c7d033 100644
--- a/.gitignore
+++ b/.gitignore
@@ -15,6 +15,11 @@
 *.xlsx
 *.zip
 
+# Notebooks shall be stored in .py or .R-format.
+# See https://adr.ssb.no/0020-lagringsformat-for-jupyter-notebooks/
+*.ipynb
+
+
 # The section below is from the GitHub .gitignore template for Python:
 # https://raw.githubusercontent.com/github/gitignore/main/Python.gitignore
 
@@ -204,18 +209,7 @@ rsconnect/
 
 # ignore poetry in .config
 .poetry/**
-/.python-version
-/.pytype/
-/docs/_build/
-
-# Visual Studio Code
-.vscode/*
-!.vscode/settings.json
-!.vscode/tasks.json
-!.vscode/launch.json
-!.vscode/extensions.json
-!.vscode/*.code-snippets
-# Local History for Visual Studio Code
-.history/
-# Built Visual Studio Code Extensions
-*.vsix
+
+# Blaise specific ignores
+*.bdix
+*.bdbx
diff --git a/docs/ssb_konjunk.rst b/docs/ssb_konjunk.rst
index 1d72a88..0ecbe8e 100644
--- a/docs/ssb_konjunk.rst
+++ b/docs/ssb_konjunk.rst
@@ -49,3 +49,11 @@ ssb\_konjunk.xml\_handling module
    :members:
    :undoc-members:
    :show-inheritance:
+   
+ssb\_konjunk.rounding module
+---------------------------------
+
+.. automodule:: ssb_konjunk.rounding
+   :members:
+   :undoc-members:
+   :show-inheritance:
diff --git a/poetry.lock b/poetry.lock
index 65a8049..d91fda0 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -1,4 +1,4 @@
-# This file is automatically @generated by Poetry 1.8.2 and should not be changed by hand.
+# This file is automatically @generated by Poetry 1.8.3 and should not be changed by hand.
 
 [[package]]
 name = "aiohappyeyeballs"
@@ -3168,6 +3168,7 @@ files = [
     {file = "PyYAML-6.0.1-cp311-cp311-win_amd64.whl", hash = "sha256:bf07ee2fef7014951eeb99f56f39c9bb4af143d8aa3c21b1677805985307da34"},
     {file = "PyYAML-6.0.1-cp312-cp312-macosx_10_9_x86_64.whl", hash = "sha256:855fb52b0dc35af121542a76b9a84f8d1cd886ea97c84703eaa6d88e37a2ad28"},
     {file = "PyYAML-6.0.1-cp312-cp312-macosx_11_0_arm64.whl", hash = "sha256:40df9b996c2b73138957fe23a16a4f0ba614f4c0efce1e9406a184b6d07fa3a9"},
+    {file = "PyYAML-6.0.1-cp312-cp312-manylinux_2_17_aarch64.manylinux2014_aarch64.whl", hash = "sha256:a08c6f0fe150303c1c6b71ebcd7213c2858041a7e01975da3a99aed1e7a378ef"},
     {file = "PyYAML-6.0.1-cp312-cp312-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:6c22bec3fbe2524cde73d7ada88f6566758a8f7227bfbf93a408a9d86bcc12a0"},
     {file = "PyYAML-6.0.1-cp312-cp312-musllinux_1_1_x86_64.whl", hash = "sha256:8d4e9c88387b0f5c7d5f281e55304de64cf7f9c0021a3525bd3b1c542da3b0e4"},
     {file = "PyYAML-6.0.1-cp312-cp312-win32.whl", hash = "sha256:d483d2cdf104e7c9fa60c544d92981f12ad66a457afae824d146093b8c294c54"},
diff --git a/pyproject.toml b/pyproject.toml
index 9cc4f0e..43f9231 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "ssb-konjunk"
-version = "0.1.9"
+version = "0.1.10"
 description = "SSB Konjunk"
 authors = ["Edvard Garmannslund <ged@ssb.no>"]
 license = "MIT"
diff --git a/src/ssb_konjunk/timestamp.py b/src/ssb_konjunk/timestamp.py
index 3e826eb..2b6a5b7 100644
--- a/src/ssb_konjunk/timestamp.py
+++ b/src/ssb_konjunk/timestamp.py
@@ -263,3 +263,26 @@ def get_ssb_timestamp(*args: int, frequency: str = "M") -> str | None:
                 return _get_timestamp_yearly(*valid_args)
             else:
                 return _get_timestamp_special(*valid_args, frequency=frequency)
+
+
+def check_periodic_year(year: int, cycle_year: int, period: int) -> bool:
+    """Check if a year is a part of a periodic cycle.
+
+    An example of use: a functionality should be performed every third
+    year, starting in year 2021. I.e. not in 2022 and 2023, but in
+    2024. Then this function should return True when passing
+    2024 as the year argument, 2021 (or 2015, 2018, 2024 and so) is
+    passed as the cycle year and period is passed as 3 (triennal period).
+
+    Args:
+        year: the year to check.
+        cycle_year: a year in the cycle.
+        period: the number of years in a period.
+
+    Returns:
+        bool: whether or not the year is part of the triennal cycle.
+    """
+    if abs(year - cycle_year) % period == 0:
+        return True
+    else:
+        return False
diff --git a/tests/test_timestamp.py b/tests/test_timestamp.py
index 1d6dc76..7d6ae9d 100644
--- a/tests/test_timestamp.py
+++ b/tests/test_timestamp.py
@@ -14,6 +14,7 @@
 from ssb_konjunk.timestamp import _get_timestamp_daily
 from ssb_konjunk.timestamp import _get_timestamp_special
 from ssb_konjunk.timestamp import _get_timestamp_yearly
+from ssb_konjunk.timestamp import check_periodic_year
 from ssb_konjunk.timestamp import get_ssb_timestamp
 
 
@@ -173,3 +174,12 @@ def test_check_valid_year() -> None:
         match=f"The order of args is start date and then end date. Therefore first year arg can not be bigger than the last. Your args are start year:{year1}  end year:{year2}.",
     ):
         _check_valid_year(year1, year2)
+
+
+def test_check_periodic_year() -> None:
+    """Test of function check_periodic_year."""
+    assert check_periodic_year(2024, 2021, 3)
+    assert not check_periodic_year(2024, 2021, 2)
+    assert check_periodic_year(2021, 2024, 3)
+    assert check_periodic_year(2021, 2021, 3)
+    assert check_periodic_year(2021, 2022, 1)