diff --git a/flopy4/mf6/codec/__init__.py b/flopy4/mf6/codec/__init__.py
index 34f14966..b9d5f05b 100644
--- a/flopy4/mf6/codec/__init__.py
+++ b/flopy4/mf6/codec/__init__.py
@@ -13,6 +13,7 @@
     unstructure_array,
     unstructure_component,
     unstructure_oc,
+    unstructure_tdis,
 )
 
 _JINJA_ENV = Environment(
@@ -40,10 +41,12 @@
 def _make_converter() -> Converter:
     from flopy4.mf6.component import Component
     from flopy4.mf6.gwf.oc import Oc
+    from flopy4.mf6.tdis import Tdis
 
     converter = Converter()
     converter.register_unstructure_hook_factory(xattree.has, lambda _: xattree.asdict)
     converter.register_unstructure_hook(Component, unstructure_component)
+    converter.register_unstructure_hook(Tdis, unstructure_tdis)
     converter.register_unstructure_hook(Oc, unstructure_oc)
     return converter
 
diff --git a/flopy4/mf6/codec/converter.py b/flopy4/mf6/codec/converter.py
index b614d713..ee0ad632 100644
--- a/flopy4/mf6/codec/converter.py
+++ b/flopy4/mf6/codec/converter.py
@@ -143,9 +143,39 @@ def unstructure_component(value: Component) -> dict[str, Any]:
     return data
 
 
+def unstructure_tdis(value: Any) -> dict[str, Any]:
+    data = xattree.asdict(value)
+    blocks = get_blocks(value.dfn)
+    for block_name, block in blocks.items():
+        if block_name == "perioddata":
+            array_fields = list(block.keys())
+
+            # Unstructure all arrays and collect all unique periods
+            arrays = {}
+            periods = set()  # type: ignore
+            for field_name in array_fields:
+                arr = unstructure_array(data.get(field_name, {}))
+                arrays[field_name] = arr
+                periods.update(arr.keys())
+            periods = sorted(periods)  # type: ignore
+
+            perioddata = {}  # type: ignore
+            for kper in periods:
+                line = []
+                for arr in arrays.values():
+                    if kper not in perioddata:
+                        perioddata[kper] = []  # type: ignore
+                    line.append(arr[kper])
+                perioddata[kper] = tuple(line)
+
+            data["perioddata"] = perioddata
+    return data
+
+
 def unstructure_oc(value: Any) -> dict[str, Any]:
     data = xattree.asdict(value)
-    for block_name, block in get_blocks(value.dfn).items():
+    blocks = get_blocks(value.dfn)
+    for block_name, block in blocks.items():
         if block_name == "period":
             # Dynamically collect all recarray fields in perioddata block
             array_fields = []
@@ -156,16 +186,15 @@ def unstructure_oc(value: Any) -> dict[str, Any]:
 
             # Unstructure all arrays and collect all unique periods
             arrays = {}
-            all_periods = set()  # type: ignore
+            periods = set()  # type: ignore
             for action, rtype, field_name in array_fields:
                 arr = unstructure_array(data.get(field_name, {}))
                 arrays[(action, rtype)] = arr
-                if isinstance(arr, dict):
-                    all_periods.update(arr.keys())
-            all_periods = sorted(all_periods)  # type: ignore
+                periods.update(arr.keys())
+            periods = sorted(periods)  # type: ignore
 
             perioddata = {}  # type: ignore
-            for kper in all_periods:
+            for kper in periods:
                 for (action, rtype), arr in arrays.items():
                     if kper in arr:
                         if kper not in perioddata:
diff --git a/flopy4/mf6/component.py b/flopy4/mf6/component.py
index 72a4b0de..78b658d0 100644
--- a/flopy4/mf6/component.py
+++ b/flopy4/mf6/component.py
@@ -100,14 +100,14 @@ def _preio(self, format: str) -> None:
             self.filename = self.default_filename()
 
     def load(self, format: str) -> None:
-        """Load the component from an input file."""
+        """Load the component and any children."""
         self._preio(format=format)
         self._load(format=format)
         for child in self.children.values():  # type: ignore
             child.load(format=format)
 
     def write(self, format: str) -> None:
-        """Write the component to an input file."""
+        """Write the component and any children."""
         self._preio(format=format)
         self._write(format=format)
         for child in self.children.values():  # type: ignore
diff --git a/flopy4/mf6/filters.py b/flopy4/mf6/filters.py
index 596a36f0..4b7d3e22 100644
--- a/flopy4/mf6/filters.py
+++ b/flopy4/mf6/filters.py
@@ -25,19 +25,17 @@ def dict_blocks(dfn: Dfn) -> dict:
     one or more fields, as opposed to a list block, which
     may only contain one recarray field, using list input.
     """
-    x = {
+    return {
         block_name: block
         for block_name, block in get_blocks(dfn).items()
         if not _is_list_block(block)
     }
-    return x
 
 
 def list_blocks(dfn: Dfn) -> dict:
-    x = {
+    return {
         block_name: block for block_name, block in get_blocks(dfn).items() if _is_list_block(block)
     }
-    return x
 
 
 def field_type(field: Field) -> str:
diff --git a/flopy4/mf6/simulation.py b/flopy4/mf6/simulation.py
index bb1203f3..46484f01 100644
--- a/flopy4/mf6/simulation.py
+++ b/flopy4/mf6/simulation.py
@@ -54,11 +54,11 @@ def run(self, exe: str | PathLike = "mf6", verbose: bool = False) -> None:
                 )
 
     def load(self, format="ascii"):
-        """Load the simulation in the specified format."""
+        """Load the simulation."""
         with cd(self.workspace):
-            super().load(format)
+            super().load(format=format)
 
     def write(self, format="ascii"):
-        """Write the simulation in the specified format."""
+        """Write the simulation."""
         with cd(self.workspace):
-            super().write(format)
+            super().write(format=format)
diff --git a/flopy4/mf6/tdis.py b/flopy4/mf6/tdis.py
index 91f3bea5..79e8396b 100644
--- a/flopy4/mf6/tdis.py
+++ b/flopy4/mf6/tdis.py
@@ -33,18 +33,21 @@ class PeriodData:
         default=1.0,
         dims=("nper",),
         converter=Converter(structure_array, takes_self=True, takes_field=True),
+        reader="urword",
     )
     nstp: NDArray[np.integer] = array(
         block="perioddata",
         default=1,
         dims=("nper",),
         converter=Converter(structure_array, takes_self=True, takes_field=True),
+        reader="urword",
     )
     tsmult: NDArray[np.floating] = array(
         block="perioddata",
         default=1.0,
         dims=("nper",),
         converter=Converter(structure_array, takes_self=True, takes_field=True),
+        reader="urword",
     )
 
     def to_time(self) -> ModelTime:
diff --git a/flopy4/mf6/templates/blocks.jinja b/flopy4/mf6/templates/blocks.jinja
index 1b0ba597..d15be65b 100644
--- a/flopy4/mf6/templates/blocks.jinja
+++ b/flopy4/mf6/templates/blocks.jinja
@@ -9,5 +9,5 @@ END {{ block_name.upper() }}
 {% endfor %}
 
 {% for block_name, block_ in (dfn|list_blocks).items() -%}
-{{ macros.list(block_name, block_) }}
+{{ macros.list(block_name, block_, stress=block_name == "period") }}
 {%- endfor%}
diff --git a/flopy4/mf6/templates/macros.jinja b/flopy4/mf6/templates/macros.jinja
index 63baf5b2..b1dc3f28 100644
--- a/flopy4/mf6/templates/macros.jinja
+++ b/flopy4/mf6/templates/macros.jinja
@@ -50,7 +50,7 @@ OPEN/CLOSE {{ value }}
 {% endif %}
 {% endmacro %}
 
-{% macro list(block_name, block) %}
+{% macro list(block_name, block, stress=False) %}
 {#
 from mf6's perspective, a list block (e.g. period data)
 always has just one variable, whose elements might be
@@ -65,8 +65,9 @@ made sure exists in a sparse dict representation of
 an array. we need to expand this into a block for
 each stress period.
 #}
-{% set dict = data[block_name] %}
-{% for kper, value in dict.items() %}
+{% set d = data[block_name] %}
+{% if stress %}
+{% for kper, value in d.items() %}
 BEGIN {{ block_name.upper() }} {{ kper }}
 {% for line in value %}
 {{ line|join(" ")|upper }}
@@ -74,4 +75,11 @@ BEGIN {{ block_name.upper() }} {{ kper }}
 END {{ block_name.upper() }} {{ kper }}
 
 {% endfor %}
+{% else %}
+BEGIN {{ block_name.upper() }}
+{% for line in d.values() %}
+{{ line|join(" ")|upper }}
+{% endfor %}
+END {{ block_name.upper() }}
+{% endif %}
 {% endmacro %}