fix: deprecate date last method (#170)

tests/test_deprecated.py

@@ -1,5 +1,7 @@
 """Test all the deprecated methods that have not been kept in the new implementation."""
 
+from datetime import datetime
+
 import pytest
 
 import geetools
@@ -17,6 +19,15 @@ def test_stretch_percentile(self):
             geetools.visualization.stretch_percentile(None, None)
 
 
+class TestDate:
+    """Test methods from the deprecated_date module."""
+
+    def test_millis_to_datetime(self):
+        with pytest.deprecated_call():
+            date = geetools.date.millisToDatetime(1527811200000)
+            assert date == datetime.strptime("2018-06-01", "%Y-%m-%d")
+
+
 class TestCollection:
     """Test methods from the deprecated_collection module."""