test(numpydates): add tests for Date to DateTime64 unit mapping

Add NumpyDates tests verifying Date conversions to DateTime64 and
InlineDateTime64 across units Y, M, D, h, m, s, ms, us, ns, comparing
against expected int values.

Covers:
- DateTime64(Date, Symbol)
- InlineDateTime64{U}(Date)
- InlineDateTime64(Date, Symbol)
and checks Dates.value and unitpair correctness.

Add test/scripts/np_dates.py to generate NumPy-based ground-truth
int64 values for selected dates.

Author: Christopher Doris

test/NumpyDates.jl

@@ -0,0 +1,101 @@
+@testitem "Date -> DateTime64/InlineDateTime64" begin
+    using Dates
+    using PythonCall: NumpyDates
+
+    # Mapping from NumPy unit symbols to NumpyDates Unit constants
+    const UNIT_CONST = Dict(
+        :Y => NumpyDates.YEARS,
+        :M => NumpyDates.MONTHS,
+        :D => NumpyDates.DAYS,
+        :h => NumpyDates.HOURS,
+        :m => NumpyDates.MINUTES,
+        :s => NumpyDates.SECONDS,
+        :ms => NumpyDates.MILLISECONDS,
+        :us => NumpyDates.MICROSECONDS,
+        :ns => NumpyDates.NANOSECONDS,
+    )
+
+    # Data generated by: uv run scripts/np_dates_all_units.py
+    # Format: (Date, unit_symbol, numpy_int_value)
+    cases = [
+        (Date(1969, 12, 31), :Y, -1),
+        (Date(1969, 12, 31), :M, -1),
+        (Date(1969, 12, 31), :D, -1),
+        (Date(1969, 12, 31), :h, -24),
+        (Date(1969, 12, 31), :m, -1440),
+        (Date(1969, 12, 31), :s, -86400),
+        (Date(1969, 12, 31), :ms, -86400000),
+        (Date(1969, 12, 31), :us, -86400000000),
+        (Date(1969, 12, 31), :ns, -86400000000000),
+        (Date(1970, 1, 1), :Y, 0),
+        (Date(1970, 1, 1), :M, 0),
+        (Date(1970, 1, 1), :D, 0),
+        (Date(1970, 1, 1), :h, 0),
+        (Date(1970, 1, 1), :m, 0),
+        (Date(1970, 1, 1), :s, 0),
+        (Date(1970, 1, 1), :ms, 0),
+        (Date(1970, 1, 1), :us, 0),
+        (Date(1970, 1, 1), :ns, 0),
+        (Date(1970, 1, 2), :Y, 0),
+        (Date(1970, 1, 2), :M, 0),
+        (Date(1970, 1, 2), :D, 1),
+        (Date(1970, 1, 2), :h, 24),
+        (Date(1970, 1, 2), :m, 1440),
+        (Date(1970, 1, 2), :s, 86400),
+        (Date(1970, 1, 2), :ms, 86400000),
+        (Date(1970, 1, 2), :us, 86400000000),
+        (Date(1970, 1, 2), :ns, 86400000000000),
+        (Date(1999, 12, 31), :Y, 29),
+        (Date(1999, 12, 31), :M, 359),
+        (Date(1999, 12, 31), :D, 10956),
+        (Date(1999, 12, 31), :h, 262944),
+        (Date(1999, 12, 31), :m, 15776640),
+        (Date(1999, 12, 31), :s, 946598400),
+        (Date(1999, 12, 31), :ms, 946598400000),
+        (Date(1999, 12, 31), :us, 946598400000000),
+        (Date(1999, 12, 31), :ns, 946598400000000000),
+        (Date(2000, 2, 29), :Y, 30),
+        (Date(2000, 2, 29), :M, 361),
+        (Date(2000, 2, 29), :D, 11016),
+        (Date(2000, 2, 29), :h, 264384),
+        (Date(2000, 2, 29), :m, 15863040),
+        (Date(2000, 2, 29), :s, 951782400),
+        (Date(2000, 2, 29), :ms, 951782400000),
+        (Date(2000, 2, 29), :us, 951782400000000),
+        (Date(2000, 2, 29), :ns, 951782400000000000),
+        (Date(1900, 1, 1), :Y, -70),
+        (Date(1900, 1, 1), :M, -840),
+        (Date(1900, 1, 1), :D, -25567),
+        (Date(1900, 1, 1), :h, -613608),
+        (Date(1900, 1, 1), :m, -36816480),
+        (Date(1900, 1, 1), :s, -2208988800),
+        (Date(1900, 1, 1), :ms, -2208988800000),
+        (Date(1900, 1, 1), :us, -2208988800000000),
+        (Date(1900, 1, 1), :ns, -2208988800000000000),
+        (Date(2100, 1, 1), :Y, 130),
+        (Date(2100, 1, 1), :M, 1560),
+        (Date(2100, 1, 1), :D, 47482),
+        (Date(2100, 1, 1), :h, 1139568),
+        (Date(2100, 1, 1), :m, 68374080),
+        (Date(2100, 1, 1), :s, 4102444800),
+        (Date(2100, 1, 1), :ms, 4102444800000),
+        (Date(2100, 1, 1), :us, 4102444800000000),
+        (Date(2100, 1, 1), :ns, 4102444800000000000),
+    ]
+
+    for (d, usym, expected) in cases
+        # 1) DateTime64 with UnitArg symbol
+        dt64 = NumpyDates.DateTime64(d, usym)
+        @test Dates.value(dt64) == expected
+
+        # 2) InlineDateTime64 with type parameter Unit constant
+        Uconst = UNIT_CONST[usym]
+        inline_typed = NumpyDates.InlineDateTime64{Uconst}(d)
+        @test Dates.value(inline_typed) == expected
+
+        # 3) InlineDateTime64 with runtime UnitArg symbol
+        inline_dyn = NumpyDates.InlineDateTime64(d, usym)
+        @test Dates.value(inline_dyn) == expected
+        @test NumpyDates.unitpair(inline_dyn) == NumpyDates.unitpair(usym)
+    end
+end

test/scripts/np_dates.py

@@ -0,0 +1,21 @@
+#!/usr/bin/env python
+import numpy as np
+
+dates = [
+    "1969-12-31",
+    "1970-01-01",
+    "1970-01-02",
+    "1999-12-31",
+    "2000-02-29",
+    "1900-01-01",
+    "2100-01-01",
+]
+
+# Note: skip 'W' to avoid week-anchor semantics; test uses floor(days/7) semantics.
+units = ["Y", "M", "D", "h", "m", "s", "ms", "us", "ns"]
+
+# Output format: "<ISO_DATE> <UNIT> <INT_VALUE>"
+for s in dates:
+    for u in units:
+        d = np.datetime64(s, u)
+        print(f"{s} {u} {int(d.astype('int64'))}")