diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
new file mode 100644
index 0000000..b142f45
--- /dev/null
+++ b/.github/workflows/build.yml
@@ -0,0 +1,54 @@
+name: Build and upload package
+
+on:
+  push:
+    branches:
+    - main
+  release:
+    types:
+    - published
+  workflow_dispatch:
+
+env:
+  FORCE_COLOR: 1
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+    name: Build & Verify package
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+      with:
+        fetch-depth: 0
+    - uses: actions/setup-python@v5
+      with:
+        python-version: 3.8
+    - run: python -m pip install --upgrade build twine
+    - run: python -m build
+    - run: twine check --strict dist/*
+    - uses: actions/upload-artifact@v4
+      with:
+        name: Packages
+        path: dist/
+
+  pypi-publish:
+    name: Publish released package to pypi.org
+    runs-on: ubuntu-latest
+    needs: build
+    if: github.event.action == 'published'
+    environment:
+      name: pypi
+      url: https://pypi.org/p/dvc
+    permissions:
+      id-token: write
+
+    steps:
+    - uses: actions/download-artifact@v4
+      with:
+        name: Packages
+        path: dist
+    - name: Upload package to PyPI
+      uses: pypa/gh-action-pypi-publish@release/v1
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..2ff3d68
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,32 @@
+name: ci
+
+on:
+  pull_request:
+  push:
+    branches: [main]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+env:
+  FORCE_COLOR: 1
+
+permissions:
+  contents: read
+
+jobs:
+  pre-commit:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+      with:
+        fetch-depth: 0
+    - uses: actions/setup-python@v5
+      with:
+        python-version: "3.8"
+    - uses: pre-commit/action@v3.0.0
+    - run: pip install .
+    - run: bscal
+    - run: bscal 2079
+    - run: bscal 2079 3
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
new file mode 100644
index 0000000..b70980f
--- /dev/null
+++ b/.pre-commit-config.yaml
@@ -0,0 +1,7 @@
+repos:
+- repo: https://github.com/astral-sh/ruff-pre-commit
+  rev: 'v0.1.9'
+  hooks:
+  - id: ruff
+    args: [--fix, --exit-non-zero-on-fix]
+  - id: ruff-format
diff --git a/bscal.py b/bscal.py
new file mode 100644
index 0000000..558e0aa
--- /dev/null
+++ b/bscal.py
@@ -0,0 +1,379 @@
+import calendar
+from datetime import date, timedelta
+from itertools import repeat
+from typing import Optional, Tuple
+
+lookup = {
+    # bs_year: [days_in_each_month, ...]
+    1970: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    1971: [31, 31, 32, 31, 32, 30, 30, 29, 30, 29, 30, 30],
+    1972: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 31],
+    1973: [30, 32, 31, 32, 31, 30, 30, 30, 29, 30, 29, 31],
+    1974: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    1975: [31, 31, 32, 32, 31, 30, 30, 29, 30, 29, 30, 30],
+    1976: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 31],
+    1977: [30, 32, 31, 32, 31, 31, 29, 30, 29, 30, 29, 31],
+    1978: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    1979: [31, 31, 32, 32, 31, 30, 30, 29, 30, 29, 30, 30],
+    1980: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 31],
+    1981: [31, 31, 31, 32, 31, 31, 29, 30, 30, 29, 30, 30],
+    1982: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    1983: [31, 31, 32, 32, 31, 30, 30, 29, 30, 29, 30, 30],
+    1984: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 31],
+    1985: [31, 31, 31, 32, 31, 31, 29, 30, 30, 29, 30, 30],
+    1986: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    1987: [31, 32, 31, 32, 31, 30, 30, 29, 30, 29, 30, 30],
+    1988: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 31],
+    1989: [31, 31, 31, 32, 31, 31, 30, 29, 30, 29, 30, 30],
+    1990: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    1991: [31, 32, 31, 32, 31, 30, 30, 29, 30, 29, 30, 30],
+    1992: [31, 32, 31, 32, 31, 30, 30, 30, 29, 30, 29, 31],
+    1993: [31, 31, 31, 32, 31, 31, 30, 29, 30, 29, 30, 30],
+    1994: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    1995: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 30],
+    1996: [31, 32, 31, 32, 31, 30, 30, 30, 29, 30, 29, 31],
+    1997: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    1998: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    1999: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 31],
+    2000: [30, 32, 31, 32, 31, 30, 30, 30, 29, 30, 29, 31],
+    2001: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    2002: [31, 31, 32, 32, 31, 30, 30, 29, 30, 29, 30, 30],
+    2003: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 31],
+    2004: [30, 32, 31, 32, 31, 30, 30, 30, 29, 30, 29, 31],
+    2005: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    2006: [31, 31, 32, 32, 31, 30, 30, 29, 30, 29, 30, 30],
+    2007: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 31],
+    2008: [31, 31, 31, 32, 31, 31, 29, 30, 30, 29, 29, 31],
+    2009: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    2010: [31, 31, 32, 32, 31, 30, 30, 29, 30, 29, 30, 30],
+    2011: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 31],
+    2012: [31, 31, 31, 32, 31, 31, 29, 30, 30, 29, 30, 30],
+    2013: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    2014: [31, 31, 32, 32, 31, 30, 30, 29, 30, 29, 30, 30],
+    2015: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 31],
+    2016: [31, 31, 31, 32, 31, 31, 29, 30, 30, 29, 30, 30],
+    2017: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    2018: [31, 32, 31, 32, 31, 30, 30, 29, 30, 29, 30, 30],
+    2019: [31, 32, 31, 32, 31, 30, 30, 30, 29, 30, 29, 31],
+    2020: [31, 31, 31, 32, 31, 31, 30, 29, 30, 29, 30, 30],
+    2021: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    2022: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 30],
+    2023: [31, 32, 31, 32, 31, 30, 30, 30, 29, 30, 29, 31],
+    2024: [31, 31, 31, 32, 31, 31, 30, 29, 30, 29, 30, 30],
+    2025: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    2026: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 31],
+    2027: [30, 32, 31, 32, 31, 30, 30, 30, 29, 30, 29, 31],
+    2028: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    2029: [31, 31, 32, 31, 32, 30, 30, 29, 30, 29, 30, 30],
+    2030: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 31],
+    2031: [30, 32, 31, 32, 31, 30, 30, 30, 29, 30, 29, 31],
+    2032: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    2033: [31, 31, 32, 32, 31, 30, 30, 29, 30, 29, 30, 30],
+    2034: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 31],
+    2035: [30, 32, 31, 32, 31, 31, 29, 30, 30, 29, 29, 31],
+    2036: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    2037: [31, 31, 32, 32, 31, 30, 30, 29, 30, 29, 30, 30],
+    2038: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 31],
+    2039: [31, 31, 31, 32, 31, 31, 29, 30, 30, 29, 30, 30],
+    2040: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    2041: [31, 31, 32, 32, 31, 30, 30, 29, 30, 29, 30, 30],
+    2042: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 31],
+    2043: [31, 31, 31, 32, 31, 31, 29, 30, 30, 29, 30, 30],
+    2044: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    2045: [31, 32, 31, 32, 31, 30, 30, 29, 30, 29, 30, 30],
+    2046: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 31],
+    2047: [31, 31, 31, 32, 31, 31, 30, 29, 30, 29, 30, 30],
+    2048: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    2049: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 30],
+    2050: [31, 32, 31, 32, 31, 30, 30, 30, 29, 30, 29, 31],
+    2051: [31, 31, 31, 32, 31, 31, 30, 29, 30, 29, 30, 30],
+    2052: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    2053: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 30],
+    2054: [31, 32, 31, 32, 31, 30, 30, 30, 29, 30, 29, 31],
+    2055: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    2056: [31, 31, 32, 31, 32, 30, 30, 29, 30, 29, 30, 30],
+    2057: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 31],
+    2058: [30, 32, 31, 32, 31, 30, 30, 30, 29, 30, 29, 31],
+    2059: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    2060: [31, 31, 32, 32, 31, 30, 30, 29, 30, 29, 30, 30],
+    2061: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 31],
+    2062: [30, 32, 31, 32, 31, 31, 29, 30, 29, 30, 29, 31],
+    2063: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    2064: [31, 31, 32, 32, 31, 30, 30, 29, 30, 29, 30, 30],
+    2065: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 31],
+    2066: [31, 31, 31, 32, 31, 31, 29, 30, 30, 29, 29, 31],
+    2067: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    2068: [31, 31, 32, 32, 31, 30, 30, 29, 30, 29, 30, 30],
+    2069: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 31],
+    2070: [31, 31, 31, 32, 31, 31, 29, 30, 30, 29, 30, 30],
+    2071: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    2072: [31, 32, 31, 32, 31, 30, 30, 29, 30, 29, 30, 30],
+    2073: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 31],
+    2074: [31, 31, 31, 32, 31, 31, 30, 29, 30, 29, 30, 30],
+    2075: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    2076: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 30],
+    2077: [31, 32, 31, 32, 31, 30, 30, 30, 29, 30, 29, 31],
+    2078: [31, 31, 31, 32, 31, 31, 30, 29, 30, 29, 30, 30],
+    2079: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    2080: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 30],
+    2081: [31, 31, 32, 32, 31, 30, 30, 30, 29, 30, 30, 30],
+    2082: [30, 32, 31, 32, 31, 30, 30, 30, 29, 30, 30, 30],
+    2083: [31, 31, 32, 31, 31, 30, 30, 30, 29, 30, 30, 30],
+    2084: [31, 31, 32, 31, 31, 30, 30, 30, 29, 30, 30, 30],
+    2085: [31, 32, 31, 32, 30, 31, 30, 30, 29, 30, 30, 30],
+    2086: [30, 32, 31, 32, 31, 30, 30, 30, 29, 30, 30, 30],
+    2087: [31, 31, 32, 31, 31, 31, 30, 30, 29, 30, 30, 30],
+    2088: [30, 31, 32, 32, 30, 31, 30, 30, 29, 30, 30, 30],
+    2089: [30, 32, 31, 32, 31, 30, 30, 30, 29, 30, 30, 30],
+    2090: [30, 32, 31, 32, 31, 30, 30, 30, 29, 30, 30, 30],
+    2091: [31, 31, 32, 32, 31, 30, 30, 29, 30, 29, 30, 30],
+    2092: [31, 31, 32, 32, 31, 30, 30, 30, 29, 30, 30, 30],
+    2093: [31, 31, 31, 32, 31, 31, 29, 30, 29, 30, 29, 31],
+    2094: [31, 31, 32, 31, 31, 30, 30, 30, 29, 30, 30, 30],
+    2095: [31, 31, 32, 32, 31, 30, 30, 29, 30, 29, 30, 30],
+    2096: [31, 32, 31, 32, 31, 30, 30, 30, 29, 29, 30, 31],
+    2097: [31, 31, 31, 32, 31, 31, 29, 30, 30, 29, 30, 30],
+    2098: [31, 31, 32, 31, 31, 31, 30, 29, 30, 29, 30, 30],
+    2099: [31, 31, 32, 31, 31, 31, 30, 29, 29, 30, 30, 30],
+    2100: [31, 32, 31, 32, 30, 31, 30, 29, 30, 29, 30, 30],
+}
+new_years = {
+    # bs_year: ad_date_for_bs_new_year
+    1970: date(1913, 4, 13),
+    1971: date(1914, 4, 13),
+    1972: date(1915, 4, 13),
+    1973: date(1916, 4, 13),
+    1974: date(1917, 4, 13),
+    1975: date(1918, 4, 13),
+    1976: date(1919, 4, 13),
+    1977: date(1920, 4, 13),
+    1978: date(1921, 4, 13),
+    1979: date(1922, 4, 13),
+    1980: date(1923, 4, 13),
+    1981: date(1924, 4, 13),
+    1982: date(1925, 4, 13),
+    1983: date(1926, 4, 13),
+    1984: date(1927, 4, 13),
+    1985: date(1928, 4, 13),
+    1986: date(1929, 4, 13),
+    1987: date(1930, 4, 13),
+    1988: date(1931, 4, 13),
+    1989: date(1932, 4, 13),
+    1990: date(1933, 4, 13),
+    1991: date(1934, 4, 13),
+    1992: date(1935, 4, 13),
+    1993: date(1936, 4, 13),
+    1994: date(1937, 4, 13),
+    1995: date(1938, 4, 13),
+    1996: date(1939, 4, 13),
+    1997: date(1940, 4, 13),
+    1998: date(1941, 4, 13),
+    1999: date(1942, 4, 13),
+    2000: date(1943, 4, 14),
+    2001: date(1944, 4, 13),
+    2002: date(1945, 4, 13),
+    2003: date(1946, 4, 13),
+    2004: date(1947, 4, 14),
+    2005: date(1948, 4, 13),
+    2006: date(1949, 4, 13),
+    2007: date(1950, 4, 13),
+    2008: date(1951, 4, 14),
+    2009: date(1952, 4, 13),
+    2010: date(1953, 4, 13),
+    2011: date(1954, 4, 13),
+    2012: date(1955, 4, 14),
+    2013: date(1956, 4, 13),
+    2014: date(1957, 4, 13),
+    2015: date(1958, 4, 13),
+    2016: date(1959, 4, 14),
+    2017: date(1960, 4, 13),
+    2018: date(1961, 4, 13),
+    2019: date(1962, 4, 13),
+    2020: date(1963, 4, 14),
+    2021: date(1964, 4, 13),
+    2022: date(1965, 4, 13),
+    2023: date(1966, 4, 13),
+    2024: date(1967, 4, 14),
+    2025: date(1968, 4, 13),
+    2026: date(1969, 4, 13),
+    2027: date(1970, 4, 14),
+    2028: date(1971, 4, 14),
+    2029: date(1972, 4, 13),
+    2030: date(1973, 4, 13),
+    2031: date(1974, 4, 14),
+    2032: date(1975, 4, 14),
+    2033: date(1976, 4, 13),
+    2034: date(1977, 4, 13),
+    2035: date(1978, 4, 14),
+    2036: date(1979, 4, 14),
+    2037: date(1980, 4, 13),
+    2038: date(1981, 4, 13),
+    2039: date(1982, 4, 14),
+    2040: date(1983, 4, 14),
+    2041: date(1984, 4, 13),
+    2042: date(1985, 4, 13),
+    2043: date(1986, 4, 14),
+    2044: date(1987, 4, 14),
+    2045: date(1988, 4, 13),
+    2046: date(1989, 4, 13),
+    2047: date(1990, 4, 14),
+    2048: date(1991, 4, 14),
+    2049: date(1992, 4, 13),
+    2050: date(1993, 4, 13),
+    2051: date(1994, 4, 14),
+    2052: date(1995, 4, 14),
+    2053: date(1996, 4, 13),
+    2054: date(1997, 4, 13),
+    2055: date(1998, 4, 14),
+    2056: date(1999, 4, 14),
+    2057: date(2000, 4, 13),
+    2058: date(2001, 4, 14),
+    2059: date(2002, 4, 14),
+    2060: date(2003, 4, 14),
+    2061: date(2004, 4, 13),
+    2062: date(2005, 4, 14),
+    2063: date(2006, 4, 14),
+    2064: date(2007, 4, 14),
+    2065: date(2008, 4, 13),
+    2066: date(2009, 4, 14),
+    2067: date(2010, 4, 14),
+    2068: date(2011, 4, 14),
+    2069: date(2012, 4, 13),
+    2070: date(2013, 4, 14),
+    2071: date(2014, 4, 14),
+    2072: date(2015, 4, 14),
+    2073: date(2016, 4, 13),
+    2074: date(2017, 4, 14),
+    2075: date(2018, 4, 14),
+    2076: date(2019, 4, 14),
+    2077: date(2020, 4, 13),
+    2078: date(2021, 4, 14),
+    2079: date(2022, 4, 14),
+    2080: date(2023, 4, 14),
+    2081: date(2024, 4, 13),
+    2082: date(2025, 4, 14),
+    2083: date(2026, 4, 14),
+    2084: date(2027, 4, 14),
+    2085: date(2028, 4, 13),
+    2086: date(2029, 4, 14),
+    2087: date(2030, 4, 14),
+    2088: date(2031, 4, 15),
+    2089: date(2032, 4, 14),
+    2090: date(2033, 4, 14),
+    2091: date(2034, 4, 14),
+    2092: date(2035, 4, 14),
+    2093: date(2036, 4, 14),
+    2094: date(2037, 4, 14),
+    2095: date(2038, 4, 14),
+    2096: date(2039, 4, 14),
+    2097: date(2040, 4, 14),
+    2098: date(2041, 4, 14),
+    2099: date(2042, 4, 14),
+    2100: date(2043, 4, 14),
+}
+
+months = [
+    "Baisakh",
+    "Jestha",
+    "Asadh",
+    "Shrawan",
+    "Bhadra",
+    "Asoj",
+    "Kartik",
+    "Mangsir",
+    "Poush",
+    "Magh",
+    "Falgun",
+    "Chaitra",
+]
+
+
+def bs_to_ad(year: int, month: int, day: int) -> date:
+    months_data = lookup[year]
+    days = sum(months_data[: month - 1]) + day - 1
+    return new_years[year] + timedelta(days)
+
+
+def ad_to_bs(ad: date, start: Optional[int] = None) -> Tuple[int, int, int]:
+    start = start or next(iter(lookup))
+    difference = ad - new_years[start]
+    for year, months_data in lookup.items():
+        if year < start:
+            continue
+        days_in_year = sum(months_data)
+        if difference.days < days_in_year:
+            break
+        difference -= timedelta(days_in_year)
+    else:
+        raise AssertionError("outside of range")  # noqa: TRY003
+
+    month = 1
+    for month, days in enumerate(months_data, start=1):  # noqa: B007
+        if difference.days < days:
+            break
+        difference -= timedelta(days)
+    return year, month, difference.days + 1
+
+
+class BSCalendar(calendar.TextCalendar):
+    def __init__(self, firstweekday: int = 0, to_highlight=()) -> None:
+        super().__init__(firstweekday)
+        self._to_highlight = to_highlight
+        self._formatting = ()
+
+    def formatmonthname(self, theyear, themonth, width, withyear=True):
+        """Return a formatted month name."""
+        s = months[themonth - 1]
+        if withyear:
+            s = f"{s} {theyear!r}"
+        return s.center(width)
+
+    def itermonthdays(self, year, month):
+        """Like itermonthdates(), but will yield day numbers. For days outside
+        the specified month the day number is 0.
+        """
+        ndays = lookup[year][month - 1]
+        day1_dt = bs_to_ad(year, month, 1)
+        day1 = day1_dt.weekday()
+        days_before = (day1 - self.firstweekday) % 7
+        yield from repeat(0, days_before)
+        yield from range(1, ndays + 1)
+        days_after = (self.firstweekday - day1 - ndays) % 7
+        yield from repeat(0, days_after)
+
+    def formatmonth(self, theyear: int, themonth: int, w: int = 0, l: int = 0) -> str:  # noqa: E741
+        self._formatting = (theyear, themonth)
+        return super().formatmonth(theyear, themonth, w, l)
+
+    def formatday(self, day: int, weekday: int, width: int) -> str:
+        s = super().formatday(day, weekday, width)
+        if (*self._formatting, day) == self._to_highlight:
+            s = f"\033[30;47m{s}\033[0m"
+        return s
+
+
+def main(args=None):
+    import argparse
+    import sys
+
+    parser = argparse.ArgumentParser()
+    parser.add_argument("year", nargs="?", type=int, help="year number (1-9999)")
+    parser.add_argument(
+        "month",
+        nargs="?",
+        type=int,
+        help="month number (1-12, text only)",
+    )
+    args = parser.parse_args(args)
+
+    year, month, day = ad_to_bs(date.today())
+    cal = BSCalendar(6, to_highlight=(year, month, day) if sys.stdout.isatty() else ())
+    if not args.year or args.month:
+        result = cal.formatmonth(args.year or year, args.month or month)
+    else:
+        result = cal.formatyear(args.year)
+    print(result)
+
+
+if __name__ == "__main__":
+    main()
diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 0000000..d83b8cd
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,36 @@
+[build-system]
+build-backend = "setuptools.build_meta"
+requires = ["setuptools>=61", "setuptools_scm[toml]>=7"]
+
+[project]
+name = "bscal"
+description = "Calendar for Bikram Sambat"
+license = { text = "Apache License 2.0" }
+requires-python = ">=3.8"
+classifiers = ["Programming Language :: Python :: 3"]
+dynamic = ["version"]
+
+[project.scripts]
+bscal = "bscal:main"
+
+[tool.setuptools]
+license-files = ["LICENSE"]
+
+[tool.setuptools_scm]
+
+[tool.ruff]
+ignore = ["ISC001"]
+select = [
+    "F", "E", "W", "C90", "I", "N", "UP", "YTT", "ASYNC", "S", "BLE", "B", "A", "C4", "T10",
+    "EXE", "ISC", "ICN", "G", "INP", "PIE", "PYI", "PT", "Q", "RSE", "RET",
+    "SLOT", "SIM", "TID", "TCH", "ARG", "PGH", "PLC", "PLE", "PLR", "PLW", "TRY",
+    "FLY", "PERF101", "RUF",
+]
+show-source = true
+show-fixes = true
+
+[tool.ruff.flake8-type-checking]
+strict = true
+
+[tool.ruff.flake8-unused-arguments]
+ignore-variadic-names = true