Added test and small date fix.

tests/test_julian.py

@@ -0,0 +1,30 @@
+# tests/test_julian.py
+
+from datetime import datetime, timezone, timedelta
+from freezegun import freeze_time
+from tools.julian import julian_date, epoch_days
+
+
+# Freeze time to exactly Jan 1, 2000, 12:00:00 UTC (The J2000 epoch)
+@freeze_time("2000-01-01 12:00:00", tz_offset=0)
+def test_julian_date_j2000():
+    # J2000 should be exactly Julian Date 2451545.0
+    jd = julian_date()
+    assert jd == 2451545.0
+
+
+@freeze_time("2000-01-01 12:00:00", tz_offset=0)
+def test_epoch_days():
+    # Since we are exactly on the epoch, days should be 0
+    days = epoch_days()
+    assert days == 0.0
+
+
+def test_julian_date_with_timezone():
+    # Create a timezone-aware datetime
+    tz = timezone(timedelta(hours=2))
+    dt = datetime(2023, 10, 15, 12, 0, 0, tzinfo=tz)
+
+    jd = julian_date(dt)
+    # 2023-10-15 12:00 GMT+2 is exactly 2460232.91666...
+    assert round(jd, 4) == 2460232.9167