@@ -1,3 +1,6 @@
+import datetime
+
+from tableauserverclient.datetime_helpers import format_datetime
 from .request_options import RequestOptions
 
 
@@ -9,6 +12,30 @@ def __init__(self, field, operator, value):
         self.value = value
 
     def __str__(self):
+        """Return the filter as a Tableau REST API filter string.
+
+        Format: ``<field>:<operator>:<value>``
+
+        Value serialization rules:
+        - datetime: ISO-8601 UTC, e.g. ``2023-01-01T00:00:00Z``.
+          Naive datetimes (no tzinfo) are rejected with ValueError; always
+          pass timezone-aware datetime objects.
+        - bool: lowercase ``true`` or ``false`` as required by the REST API.
+        - list: bracket-enclosed comma-separated values, e.g. ``[a,b,c]``.
+          Only valid with the ``in`` operator.
+        - All other types: ``str()`` of the value.
+        """
+        if isinstance(self._value, datetime.datetime):
+            if self._value.tzinfo is None:
+                raise ValueError(
+                    "Naive datetime passed to Filter; Tableau Server requires UTC. "
+                    "Use a timezone-aware datetime, e.g. "
+                    "datetime.datetime(..., tzinfo=datetime.timezone.utc)."
+                )
+            return f"{self.field}:{self.operator}:{format_datetime(self._value)}"
+        if isinstance(self._value, bool):
+            # Tableau REST API requires lowercase 'true'/'false', not Python's 'True'/'False'
+            return f"{self.field}:{self.operator}:{str(self._value).lower()}"
         value_string = str(self._value)
         if isinstance(self._value, list):
             # this should turn the string representation of the list
 
@@ -1,3 +1,5 @@
+import datetime
+
 import tableauserverclient as TSC
 
 
@@ -14,3 +16,110 @@ def test_filter_in():
     filter = TSC.Filter(TSC.RequestOptions.Field.Name, TSC.RequestOptions.Operator.In, projects_to_find)
 
     assert str(filter) == "name:in:[default,Salesforce Sales Projeśt]"
+
+
+def test_filter_in_single_value():
+    """A single-element list produces valid bracket syntax."""
+    filter = TSC.Filter(TSC.RequestOptions.Field.Tags, TSC.RequestOptions.Operator.In, ["sample"])
+
+    assert str(filter) == "tags:in:[sample]"
+
+
+def test_filter_in_multiple_values():
+    """Multi-element list produces comma-separated values inside brackets."""
+    filter = TSC.Filter(TSC.RequestOptions.Field.Tags, TSC.RequestOptions.Operator.In, ["a", "b", "c"])
+
+    assert str(filter) == "tags:in:[a,b,c]"
+
+
+def test_filter_integer_value():
+    """Integer filter values are serialized as plain decimal strings."""
+    filter = TSC.Filter(TSC.RequestOptions.Field.Size, TSC.RequestOptions.Operator.GreaterThan, 0)
+
+    assert str(filter) == "size:gt:0"
+
+
+def test_filter_integer_nonzero():
+    filter = TSC.Filter(TSC.RequestOptions.Field.SheetCount, TSC.RequestOptions.Operator.GreaterThanOrEqual, 5)
+
+    assert str(filter) == "sheetCount:gte:5"
+
+
+def test_filter_date_no_encoding():
+    """Date filter values should not have colons pre-encoded (fixes #1025).
+
+    The requests library handles URL encoding of the whole filter parameter,
+    so pre-encoding colons in datetime values causes double-encoding on the wire.
+    """
+    utc = datetime.timezone.utc
+    dt = datetime.datetime(2023, 1, 1, 0, 0, 0, tzinfo=utc)
+    filter = TSC.Filter(TSC.RequestOptions.Field.CreatedAt, TSC.RequestOptions.Operator.LessThan, dt)
+
+    result = str(filter)
+    assert result == "createdAt:lt:2023-01-01T00:00:00Z"
+    assert "%3A" not in result, "Colons in datetime values must not be percent-encoded"
+
+
+def test_filter_date_uses_tableau_format():
+    """Datetime values are serialized in Tableau ISO-8601 format, not Python default."""
+    utc = datetime.timezone.utc
+    dt = datetime.datetime(2024, 6, 15, 12, 30, 45, tzinfo=utc)
+    filter = TSC.Filter(TSC.RequestOptions.Field.UpdatedAt, TSC.RequestOptions.Operator.GreaterThan, dt)
+
+    result = str(filter)
+    # Must use 'T' separator and 'Z' suffix, not Python's space-separated format
+    assert result == "updatedAt:gt:2024-06-15T12:30:45Z"
+    assert " " not in result.split(":", 2)[2], "Datetime value must not contain a space (Python default format)"
+
+
+def test_filter_date_non_utc_converted():
+    """Non-UTC datetime values are converted to UTC before serialization."""
+    eastern = datetime.timezone(datetime.timedelta(hours=-5))
+    dt = datetime.datetime(2023, 3, 10, 12, 0, 0, tzinfo=eastern)
+    filter = TSC.Filter(TSC.RequestOptions.Field.CreatedAt, TSC.RequestOptions.Operator.Equals, dt)
+
+    result = str(filter)
+    assert result == "createdAt:eq:2023-03-10T17:00:00Z"
+
+
+def test_filter_bool_true():
+    """Boolean True is serialized as lowercase 'true' for Tableau REST API."""
+    filter = TSC.Filter(TSC.RequestOptions.Field.IsCertified, TSC.RequestOptions.Operator.Equals, True)
+
+    result = str(filter)
+    assert result == "isCertified:eq:true"
+    assert "True" not in result, "Boolean True must be lowercase 'true'"
+
+
+def test_filter_bool_false():
+    """Boolean False is serialized as lowercase 'false' for Tableau REST API."""
+    filter = TSC.Filter(TSC.RequestOptions.Field.IsCertified, TSC.RequestOptions.Operator.Equals, False)
+
+    result = str(filter)
+    assert result == "isCertified:eq:false"
+    assert "False" not in result, "Boolean False must be lowercase 'false'"
+
+
+def test_filter_bool_has_extracts():
+    """Boolean filter works for hasExtracts field."""
+    filter = TSC.Filter(TSC.RequestOptions.Field.HasExtracts, TSC.RequestOptions.Operator.Equals, True)
+
+    assert str(filter) == "hasExtracts:eq:true"
+
+
+def test_filter_date_naive_raises():
+    """A naive datetime (no tzinfo) raises ValueError with a helpful message."""
+    import pytest
+
+    naive_dt = datetime.datetime(2023, 1, 1, 12, 0, 0)  # no tzinfo
+    f = TSC.Filter(TSC.RequestOptions.Field.CreatedAt, TSC.RequestOptions.Operator.Equals, naive_dt)
+    with pytest.raises(ValueError, match="Naive datetime"):
+        str(f)
+
+
+def test_filter_list_rejects_non_in_operator():
+    """A list value with a non-In operator raises ValueError."""
+    import pytest
+
+    with pytest.raises(ValueError):
+        TSC.Filter(TSC.RequestOptions.Field.Tags, TSC.RequestOptions.Operator.Equals, ["a", "b"])