diff --git a/src/blenderbim/blenderbim/bim/module/sequence/__init__.py b/src/blenderbim/blenderbim/bim/module/sequence/__init__.py
index 8fbc13bdb3..45f1f6b15b 100644
--- a/src/blenderbim/blenderbim/bim/module/sequence/__init__.py
+++ b/src/blenderbim/blenderbim/bim/module/sequence/__init__.py
@@ -17,13 +17,21 @@ classes = (
     operator.EnableEditingTasks,
     operator.DisableEditingWorkSchedule,
     operator.DisableTaskEditingUI,
-    operator.LoadWorkCalendars,
-    operator.DisableWorkCalendarEditingUI,
     operator.AddWorkCalendar,
     operator.EditWorkCalendar,
+    operator.EditWorkTime,
     operator.RemoveWorkCalendar,
+    operator.RemoveWorkTime,
+    operator.UnassignRecurrencePattern,
+    operator.RemoveTimePeriod,
     operator.EnableEditingWorkCalendar,
+    operator.EnableEditingWorkTime,
+    operator.EnableEditingWorkCalendarTimes,
     operator.DisableEditingWorkCalendar,
+    operator.DisableEditingWorkTime,
+    operator.AddWorkTime,
+    operator.AssignRecurrencePattern,
+    operator.AddTimePeriod,
     operator.AddTask,
     operator.AddSummaryTask,
     operator.ExpandTask,
@@ -54,7 +62,6 @@ classes = (
     ui.BIM_PT_work_plans,
     ui.BIM_PT_work_schedules,
     ui.BIM_PT_work_calendars,
-    ui.BIM_UL_work_calendars,
     ui.BIM_UL_tasks,
 )
 
diff --git a/src/blenderbim/blenderbim/bim/module/sequence/operator.py b/src/blenderbim/blenderbim/bim/module/sequence/operator.py
index 283621494c..6cb69430d0 100644
--- a/src/blenderbim/blenderbim/bim/module/sequence/operator.py
+++ b/src/blenderbim/blenderbim/bim/module/sequence/operator.py
@@ -747,32 +747,6 @@ class GenerateGanttChart(bpy.types.Operator):
             self.create_new_task_json(task_id)
 
 
-class LoadWorkCalendars(bpy.types.Operator):
-    bl_idname = "bim.load_work_calendars"
-    bl_label = "Load Work Calendars"
-
-    def execute(self, context):
-        props = context.scene.BIMWorkCalendarProperties
-        while len(props.work_calendars) > 0:
-            props.work_calendars.remove(0)
-        for ifc_definition_id, work_calendar in Data.work_calendars.items():
-            new = props.work_calendars.add()
-            new.ifc_definition_id = ifc_definition_id
-            new.name = work_calendar["Name"] or "Unnamed"
-        props.is_editing = True
-        bpy.ops.bim.disable_editing_work_calendar()
-        return {"FINISHED"}
-
-
-class DisableWorkCalendarEditingUI(bpy.types.Operator):
-    bl_idname = "bim.disable_work_calendar_editing_ui"
-    bl_label = "Disable WorkCalendar Editing UI"
-
-    def execute(self, context):
-        context.scene.BIMWorkCalendarProperties.is_editing = False
-        return {"FINISHED"}
-
-
 class AddWorkCalendar(bpy.types.Operator):
     bl_idname = "bim.add_work_calendar"
     bl_label = "Add Work Calendar"
@@ -780,7 +754,6 @@ class AddWorkCalendar(bpy.types.Operator):
     def execute(self, context):
         ifcopenshell.api.run("sequence.add_work_calendar", IfcStore.get_file())
         Data.load(IfcStore.get_file())
-        bpy.ops.bim.load_work_calendars()
         return {"FINISHED"}
 
 
@@ -806,7 +779,7 @@ class EditWorkCalendar(bpy.types.Operator):
             **{"work_calendar": self.file.by_id(props.active_work_calendar_id), "attributes": attributes},
         )
         Data.load(IfcStore.get_file())
-        bpy.ops.bim.load_work_calendars()
+        bpy.ops.bim.disable_editing_work_calendar()
         return {"FINISHED"}
 
 
@@ -821,13 +794,12 @@ class RemoveWorkCalendar(bpy.types.Operator):
             "sequence.remove_work_calendar", self.file, **{"work_calendar": self.file.by_id(self.work_calendar)}
         )
         Data.load(self.file)
-        bpy.ops.bim.load_work_calendars()
         return {"FINISHED"}
 
 
 class EnableEditingWorkCalendar(bpy.types.Operator):
     bl_idname = "bim.enable_editing_work_calendar"
-    bl_label = "Enable Editing Work Plan"
+    bl_label = "Enable Editing Work Calendar"
     work_calendar: bpy.props.IntProperty()
 
     def execute(self, context):
@@ -853,6 +825,7 @@ class EnableEditingWorkCalendar(bpy.types.Operator):
                 if data[attribute.name()]:
                     new.enum_value = data[attribute.name()]
         props.active_work_calendar_id = self.work_calendar
+        props.is_editing = "ATTRIBUTES"
         return {"FINISHED"}
 
 
@@ -884,3 +857,182 @@ class ImportP6(bpy.types.Operator, ImportHelper):
         Data.load(IfcStore.get_file())
         print("Import finished in {:.2f} seconds".format(time.time() - start))
         return {"FINISHED"}
+
+
+class EnableEditingWorkCalendarTimes(bpy.types.Operator):
+    bl_idname = "bim.enable_editing_work_calendar_times"
+    bl_label = "Enable Editing Work Calendar Times"
+    work_calendar: bpy.props.IntProperty()
+
+    def execute(self, context):
+        props = context.scene.BIMWorkCalendarProperties
+        props.active_work_calendar_id = self.work_calendar
+        props.is_editing = "WORKTIMES"
+        return {"FINISHED"}
+
+
+class AddWorkTime(bpy.types.Operator):
+    bl_idname = "bim.add_work_time"
+    bl_label = "Add Work Time"
+    work_calendar: bpy.props.IntProperty()
+    time_type: bpy.props.StringProperty()
+
+    def execute(self, context):
+        self.file = IfcStore.get_file()
+        ifcopenshell.api.run(
+            "sequence.add_work_time",
+            self.file,
+            **{"work_calendar": self.file.by_id(self.work_calendar), "time_type": self.time_type},
+        )
+        Data.load(IfcStore.get_file())
+        return {"FINISHED"}
+
+
+class EnableEditingWorkTime(bpy.types.Operator):
+    bl_idname = "bim.enable_editing_work_time"
+    bl_label = "Enable Editing Work Time"
+    work_time: bpy.props.IntProperty()
+
+    def execute(self, context):
+        props = context.scene.BIMWorkCalendarProperties
+        while len(props.work_time_attributes) > 0:
+            props.work_time_attributes.remove(0)
+
+        data = Data.work_times[self.work_time]
+
+        for attribute in IfcStore.get_schema().declaration_by_name("IfcWorkTime").all_attributes():
+            data_type = ifcopenshell.util.attribute.get_primitive_type(attribute)
+            if data_type == "entity":
+                continue
+            new = props.work_time_attributes.add()
+            new.name = attribute.name()
+            new.is_null = data[attribute.name()] is None
+            new.is_optional = attribute.optional()
+            new.data_type = data_type
+            if attribute.name() in ["Start", "Finish"]:
+                new.string_value = "" if new.is_null else data[attribute.name()].isoformat()
+            elif data_type == "string":
+                new.string_value = "" if new.is_null else data[attribute.name()]
+            elif data_type == "enum":
+                new.enum_items = json.dumps(ifcopenshell.util.attribute.get_enum_items(attribute))
+                if data[attribute.name()]:
+                    new.enum_value = data[attribute.name()]
+        props.active_work_time_id = self.work_time
+        return {"FINISHED"}
+
+
+class DisableEditingWorkTime(bpy.types.Operator):
+    bl_idname = "bim.disable_editing_work_time"
+    bl_label = "Disable Editing Work Time"
+
+    def execute(self, context):
+        context.scene.BIMWorkCalendarProperties.active_work_time_id = 0
+        return {"FINISHED"}
+
+
+class EditWorkTime(bpy.types.Operator):
+    bl_idname = "bim.edit_work_time"
+    bl_label = "Edit Work Time"
+
+    def execute(self, context):
+        props = context.scene.BIMWorkCalendarProperties
+        attributes = {}
+        for attribute in props.work_time_attributes:
+            if attribute.is_null:
+                attributes[attribute.name] = None
+            else:
+                if attribute.data_type == "string":
+                    attributes[attribute.name] = attribute.string_value
+                elif attribute.data_type == "enum":
+                    attributes[attribute.name] = attribute.enum_value
+        self.file = IfcStore.get_file()
+        ifcopenshell.api.run(
+            "sequence.edit_work_time",
+            self.file,
+            **{"work_time": self.file.by_id(props.active_work_time_id), "attributes": attributes},
+        )
+        Data.load(IfcStore.get_file())
+        bpy.ops.bim.disable_editing_work_time()
+        return {"FINISHED"}
+
+
+class RemoveWorkTime(bpy.types.Operator):
+    bl_idname = "bim.remove_work_time"
+    bl_label = "Remove Work Plan"
+    work_time: bpy.props.IntProperty()
+
+    def execute(self, context):
+        self.file = IfcStore.get_file()
+        ifcopenshell.api.run("sequence.remove_work_time", self.file, **{"work_time": self.file.by_id(self.work_time)})
+        Data.load(self.file)
+        return {"FINISHED"}
+
+
+class AssignRecurrencePattern(bpy.types.Operator):
+    bl_idname = "bim.assign_recurrence_pattern"
+    bl_label = "Assign Recurrence Pattern"
+    work_time: bpy.props.IntProperty()
+    recurrence_type: bpy.props.StringProperty()
+
+    def execute(self, context):
+        self.file = IfcStore.get_file()
+        ifcopenshell.api.run(
+            "sequence.assign_recurrence_pattern",
+            self.file,
+            **{"parent": self.file.by_id(self.work_time), "recurrence_type": self.recurrence_type},
+        )
+        Data.load(IfcStore.get_file())
+        return {"FINISHED"}
+
+
+class UnassignRecurrencePattern(bpy.types.Operator):
+    bl_idname = "bim.unassign_recurrence_pattern"
+    bl_label = "Unassign Recurrence Pattern"
+    recurrence_pattern: bpy.props.IntProperty()
+
+    def execute(self, context):
+        self.file = IfcStore.get_file()
+        ifcopenshell.api.run(
+            "sequence.unassign_recurrence_pattern",
+            self.file,
+            **{"recurrence_pattern": self.file.by_id(self.recurrence_pattern)},
+        )
+        Data.load(self.file)
+        return {"FINISHED"}
+
+
+class AddTimePeriod(bpy.types.Operator):
+    bl_idname = "bim.add_time_period"
+    bl_label = "Add Time Period"
+    recurrence_pattern: bpy.props.IntProperty()
+
+    def execute(self, context):
+        self.props = context.scene.BIMWorkCalendarProperties
+        self.file = IfcStore.get_file()
+        ifcopenshell.api.run(
+            "sequence.add_time_period",
+            self.file,
+            **{
+                "recurrence_pattern": self.file.by_id(self.recurrence_pattern),
+                "start_time": self.props.start_time,
+                "end_time": self.props.start_time,
+            },
+        )
+        Data.load(IfcStore.get_file())
+        return {"FINISHED"}
+
+
+class RemoveTimePeriod(bpy.types.Operator):
+    bl_idname = "bim.remove_time_period"
+    bl_label = "Remove Time Period"
+    time_period: bpy.props.IntProperty()
+
+    def execute(self, context):
+        self.file = IfcStore.get_file()
+        ifcopenshell.api.run(
+            "sequence.remove_time_period",
+            self.file,
+            **{"time_period": self.file.by_id(self.time_period)},
+        )
+        Data.load(self.file)
+        return {"FINISHED"}
diff --git a/src/blenderbim/blenderbim/bim/module/sequence/prop.py b/src/blenderbim/blenderbim/bim/module/sequence/prop.py
index cd8a589eb7..15a25f33d6 100644
--- a/src/blenderbim/blenderbim/bim/module/sequence/prop.py
+++ b/src/blenderbim/blenderbim/bim/module/sequence/prop.py
@@ -170,7 +170,30 @@ class WorkCalendar(PropertyGroup):
 
 class BIMWorkCalendarProperties(PropertyGroup):
     work_calendar_attributes: CollectionProperty(name="Work Calendar Attributes", type=Attribute)
-    is_editing: BoolProperty(name="Is Editing", default=False)
+    work_time_attributes: CollectionProperty(name="Work Time Attributes", type=Attribute)
+    is_editing: StringProperty(name="Is Editing")
     work_calendars: CollectionProperty(name="Work Calendar", type=WorkCalendar)
-    active_work_calendar_index: IntProperty(name="Active Work Calendar Index")
     active_work_calendar_id: IntProperty(name="Active Work Calendar Id")
+    active_work_time_id: IntProperty(name="Active Work Time Id")
+    weekday_component_monday: BoolProperty(name="M")
+    weekday_component_tuesday: BoolProperty(name="T")
+    weekday_component_wednesday: BoolProperty(name="W")
+    weekday_component_thursday: BoolProperty(name="T")
+    weekday_component_friday: BoolProperty(name="F")
+    weekday_component_saturday: BoolProperty(name="S")
+    weekday_component_sunday: BoolProperty(name="S")
+    dummy_bool: BoolProperty(name="Active Work Calendar Id")
+    dummy_int: IntProperty(name="Active Work Calendar Id")
+    recurrence_types: EnumProperty(items=[
+        ("DAILY", "Daily", "e.g. Every day"),
+        ("WEEKLY", "Weekly", "e.g. Every Friday"),
+        ("MONTHLY_BY_DAY_OF_MONTH", "Monthly on Specified Date", "e.g. Every 2nd of each Month"),
+        ("MONTHLY_BY_POSITION", "Monthly on Specified Weekday", "e.g. Every 1st Friday of each Month"),
+        # https://forums.buildingsmart.org/t/what-does-by-day-count-and-by-weekday-count-mean-in-ifcrecurrencetypeenum/3571
+        # ("BY_DAY_COUNT", "", ""),
+        # ("BY_WEEKDAY_COUNT", "", ""),
+        ("YEARLY_BY_DAY_OF_MONTH", "Yearly on Specified Date", "e.g. Every 2nd of October"),
+        ("YEARLY_BY_POSITION", "Yearly on Specified Weekday", "e.g. Every 1st Friday of October"),
+    ], name="Recurrence Types")
+    start_time: StringProperty(name="Start Time")
+    end_time: StringProperty(name="End Time")
diff --git a/src/blenderbim/blenderbim/bim/module/sequence/ui.py b/src/blenderbim/blenderbim/bim/module/sequence/ui.py
index c4381f5ba0..a395eedb1c 100644
--- a/src/blenderbim/blenderbim/bim/module/sequence/ui.py
+++ b/src/blenderbim/blenderbim/bim/module/sequence/ui.py
@@ -266,29 +266,69 @@ class BIM_PT_work_calendars(Panel):
         if not Data.is_loaded:
             Data.load(IfcStore.get_file())
         self.props = context.scene.BIMWorkCalendarProperties
+
+        row = self.layout.row()
+        row.operator("bim.add_work_calendar", icon="ADD")
+
+        for work_calendar_id, work_calendar in Data.work_calendars.items():
+            self.draw_work_calendar_ui(work_calendar_id, work_calendar)
+
+    def draw_work_calendar_ui(self, work_calendar_id, work_calendar):
         row = self.layout.row(align=True)
-        row.label(text="{} Work Calendar Found".format(len(Data.work_calendars)), icon="TEXT")
-        if self.props.is_editing:
-            row.operator("bim.add_work_calendar", text="", icon="ADD")
-            row.operator("bim.disable_work_calendar_editing_ui", text="", icon="CHECKMARK")
+        row.label(text=work_calendar["Name"] or "Unnamed", icon="VIEW_ORTHO")
+        if self.props.active_work_calendar_id == work_calendar_id:
+            row.operator("bim.edit_work_calendar", text="", icon="CHECKMARK")
+            row.operator("bim.disable_editing_work_calendar", text="", icon="CANCEL")
+        elif self.props.active_work_calendar_id:
+            row.operator("bim.remove_work_calendar", text="", icon="X").work_calendar = work_calendar_id
         else:
-            row.operator("bim.load_work_calendars", text="", icon="GREASEPENCIL")
+            op = row.operator("bim.enable_editing_work_calendar_times", text="", icon="MESH_GRID")
+            op.work_calendar = work_calendar_id
+            op = row.operator("bim.enable_editing_work_calendar", text="", icon="GREASEPENCIL")
+            op.work_calendar = work_calendar_id
+            row.operator("bim.remove_work_calendar", text="", icon="X").work_calendar = work_calendar_id
 
-        if self.props.is_editing:
-            self.layout.template_list(
-                "BIM_UL_work_calendars",
-                "",
-                self.props,
-                "work_calendars",
-                self.props,
-                "active_work_calendar_index",
-            )
+        if self.props.active_work_calendar_id == work_calendar_id:
+            if self.props.is_editing == "ATTRIBUTES":
+                self.draw_editable_ui()
+            elif self.props.is_editing == "WORKTIMES":
+                self.draw_work_times_ui(work_calendar_id, work_calendar)
 
-        if self.props.active_work_calendar_id:
-            self.draw_editable_ui(context)
+    def draw_work_times_ui(self, work_calendar_id, work_calendar):
+        row = self.layout.row(align=True)
+        op = row.operator("bim.add_work_time", text="Add Work Time", icon="ADD")
+        op.work_calendar = work_calendar_id
+        op.time_type = "WorkingTimes"
+        op = row.operator("bim.add_work_time", text="Add Exception Time", icon="ADD")
+        op.work_calendar = work_calendar_id
+        op.time_type = "ExceptionTimes"
 
-    def draw_editable_ui(self, context):
-        for attribute in self.props.work_calendar_attributes:
+        for work_time_id in work_calendar["WorkingTimes"]:
+            self.draw_work_time_ui(Data.work_times[work_time_id], time_type="WorkingTimes")
+
+        for work_time_id in work_calendar["ExceptionTimes"]:
+            self.draw_work_time_ui(Data.work_times[work_time_id], time_type="ExceptionTimes")
+
+    def draw_work_time_ui(self, work_time, time_type):
+        row = self.layout.row(align=True)
+        row.label(text=work_time["Name"] or "Unnamed", icon="MESH_GRID" if time_type == "WorkingTimes" else "LIGHTPROBE_GRID")
+        if self.props.active_work_time_id == work_time["id"]:
+            row.operator("bim.edit_work_time", text="", icon="CHECKMARK")
+            row.operator("bim.disable_editing_work_time", text="", icon="CANCEL")
+        elif self.props.active_work_time_id:
+            op = row.operator("bim.remove_work_time", text="", icon="X")
+            op.work_time = work_time["id"]
+        else:
+            op = row.operator("bim.enable_editing_work_time", text="", icon="GREASEPENCIL")
+            op.work_time = work_time["id"]
+            op = row.operator("bim.remove_work_time", text="", icon="X")
+            op.work_time = work_time["id"]
+
+        if self.props.active_work_time_id == work_time["id"]:
+            self.draw_editable_work_time_ui(work_time)
+
+    def draw_editable_work_time_ui(self, work_time):
+        for attribute in self.props.work_time_attributes:
             row = self.layout.row(align=True)
             if attribute.data_type == "string":
                 row.prop(attribute, "string_value", text=attribute.name)
@@ -297,18 +337,59 @@ class BIM_PT_work_calendars(Panel):
             if attribute.is_optional:
                 row.prop(attribute, "is_null", icon="RADIOBUT_OFF" if attribute.is_null else "RADIOBUT_ON", text="")
 
+        if work_time["RecurrencePattern"]:
+            self.draw_editable_recurrence_pattern_ui(Data.recurrence_patterns[work_time["RecurrencePattern"]])
+        else:
+            row = self.layout.row(align=True)
+            row.prop(self.props, "recurrence_types", icon="RECOVER_LAST", text="")
+            op = row.operator("bim.assign_recurrence_pattern", icon="ADD", text="")
+            op.work_time = work_time["id"]
+            op.recurrence_type = self.props.recurrence_types
 
-class BIM_UL_work_calendars(UIList):
-    def draw_item(self, context, layout, data, item, icon, active_data, active_propname):
-        if item:
-            row = layout.row(align=True)
-            row.label(text=item.name)
-            if context.scene.BIMWorkCalendarProperties.active_work_calendar_id == item.ifc_definition_id:
-                row.operator("bim.edit_work_calendar", text="", icon="CHECKMARK")
-                row.operator("bim.disable_editing_work_calendar", text="", icon="X")
-            elif context.scene.BIMWorkCalendarProperties.active_work_calendar_id:
-                row.operator("bim.remove_work_calendar", text="", icon="X").work_calendar = item.ifc_definition_id
-            else:
-                op = row.operator("bim.enable_editing_work_calendar", text="", icon="GREASEPENCIL")
-                op.work_calendar = item.ifc_definition_id
-                row.operator("bim.remove_work_calendar", text="", icon="X").work_calendar = item.ifc_definition_id
+    def draw_editable_recurrence_pattern_ui(self, recurrence_pattern):
+        box = self.layout.box()
+        row = box.row(align=True)
+        row.label(text=recurrence_pattern["RecurrenceType"], icon="RECOVER_LAST")
+        op = row.operator("bim.unassign_recurrence_pattern", text="", icon="X")
+        op.recurrence_pattern = recurrence_pattern["id"]
+
+        row = box.row(align=True)
+        row.prop(self.props, "start_time", text="")
+        row.prop(self.props, "end_time", text="")
+        op = row.operator("bim.add_time_period", text="", icon="ADD")
+        op.recurrence_pattern = recurrence_pattern["id"]
+
+        for time_period_id in recurrence_pattern["TimePeriods"]:
+            time_period = Data.time_periods[time_period_id]
+            row = box.row(align=True)
+            row.label(text="{} - {}".format(time_period["StartTime"], time_period["EndTime"]), icon="TIME")
+            op = row.operator("bim.remove_time_period", text="", icon="X")
+            op.time_period = time_period_id
+
+        if recurrence_pattern["RecurrenceType"] == "DAILY":
+            pass # No need to show any custom UI
+        if recurrence_pattern["RecurrenceType"] == "WEEKLY":
+            row = box.row(align=True)
+            row.prop(self.props, "weekday_component_monday", text="M")
+            row.prop(self.props, "weekday_component_tuesday", text="T")
+            row.prop(self.props, "weekday_component_wednesday", text="W")
+            row.prop(self.props, "weekday_component_thursday", text="T")
+            row.prop(self.props, "weekday_component_friday", text="F")
+            row.prop(self.props, "weekday_component_saturday", text="S")
+            row.prop(self.props, "weekday_component_sunday", text="S")
+
+        row = box.row(align=True)
+        row.prop(self.props, "dummy_int", text="Recurrence Interval")
+        row = box.row(align=True)
+        row.prop(self.props, "dummy_int", text="Occurs N Times")
+
+
+    def draw_editable_ui(self):
+        for attribute in self.props.work_calendar_attributes:
+            row = self.layout.row(align=True)
+            if attribute.data_type == "string":
+                row.prop(attribute, "string_value", text=attribute.name)
+            elif attribute.data_type == "enum":
+                row.prop(attribute, "enum_value", text=attribute.name)
+            if attribute.is_optional:
+                row.prop(attribute, "is_null", icon="RADIOBUT_OFF" if attribute.is_null else "RADIOBUT_ON", text="")
diff --git a/src/ifcopenshell-python/ifcopenshell/api/sequence/add_time_period.py b/src/ifcopenshell-python/ifcopenshell/api/sequence/add_time_period.py
new file mode 100644
index 0000000000..a323a6a553
--- /dev/null
+++ b/src/ifcopenshell-python/ifcopenshell/api/sequence/add_time_period.py
@@ -0,0 +1,25 @@
+import ifcopenshell.api
+import ifcopenshell.util.date
+from datetime import datetime
+from datetime import timedelta
+
+
+class Usecase:
+    def __init__(self, file, **settings):
+        self.file = file
+        self.settings = {
+            "recurrence_pattern": None,
+            "start_time": None,
+            "end_time": None,
+        }
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        time_period = self.file.create_entity("IfcTimePeriod")
+        time_period.StartTime = ifcopenshell.util.date.datetime2ifc(self.settings["start_time"], "IfcTime")
+        time_period.EndTime = ifcopenshell.util.date.datetime2ifc(self.settings["end_time"], "IfcTime")
+        time_periods = list(self.settings["recurrence_pattern"].TimePeriods or [])
+        time_periods.append(time_period)
+        self.settings["recurrence_pattern"].TimePeriods = time_periods
+        return time_period
diff --git a/src/ifcopenshell-python/ifcopenshell/api/sequence/add_work_time.py b/src/ifcopenshell-python/ifcopenshell/api/sequence/add_work_time.py
index 40589b5098..c05eb3085e 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/sequence/add_work_time.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/sequence/add_work_time.py
@@ -1,17 +1,17 @@
 class Usecase:
     def __init__(self, file, **settings):
         self.file = file
-        self.settings = {"work_calendar": None, "type": "WorkingTimes", "name": None}
+        self.settings = {"work_calendar": None, "time_type": None}
         for key, value in settings.items():
             self.settings[key] = value
 
     def execute(self):
-        work_time = self.file.create_entity("IfcWorkTime", **{"Name": self.settings["name"]})
-        if self.settings["type"] == "WorkingTimes":
+        work_time = self.file.create_entity("IfcWorkTime")
+        if self.settings["time_type"] == "WorkingTimes":
             working_times = list(self.settings["work_calendar"].WorkingTimes or [])
             working_times.append(work_time)
             self.settings["work_calendar"].WorkingTimes = working_times
-        elif self.settings["type"] == "ExceptionTimes":
+        elif self.settings["time_type"] == "ExceptionTimes":
             exception_times = list(self.settings["work_calendar"].ExceptionTimes or [])
             exception_times.append(work_time)
             self.settings["work_calendar"].ExceptionTimes = exception_times
diff --git a/src/ifcopenshell-python/ifcopenshell/api/time/add_recurrence_pattern.py b/src/ifcopenshell-python/ifcopenshell/api/sequence/assign_recurrence_pattern.py
similarity index 76%
rename from src/ifcopenshell-python/ifcopenshell/api/time/add_recurrence_pattern.py
rename to src/ifcopenshell-python/ifcopenshell/api/sequence/assign_recurrence_pattern.py
index ec6883dc7d..9cbd7f1669 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/time/add_recurrence_pattern.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/sequence/assign_recurrence_pattern.py
@@ -8,8 +8,11 @@ class Usecase:
     def execute(self):
         recurrence = self.file.createIfcRecurrencePattern(self.settings["recurrence_type"])
 
-        if self.settings["parent"].is_a("IfcWorkTime") and self.settings["parent"].RecurrencePattern:
-            if len(self.file.get_inverse(self.settings["parent"].RecurrencePattern)) == 1:
+        if self.settings["parent"].is_a("IfcWorkTime"):
+            if (
+                self.settings["parent"].RecurrencePattern
+                and len(self.file.get_inverse(self.settings["parent"].RecurrencePattern)) == 1
+            ):
                 self.file.remove(self.settings["parent"].RecurrencePattern)
             self.settings["parent"].RecurrencePattern = recurrence
         elif self.settings["parent"].is_a("IfcTaskTimeRecurring"):
diff --git a/src/ifcopenshell-python/ifcopenshell/api/sequence/data.py b/src/ifcopenshell-python/ifcopenshell/api/sequence/data.py
index 0333c524b3..5f7ad96676 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/sequence/data.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/sequence/data.py
@@ -5,6 +5,10 @@ class Data:
     is_loaded = False
     work_plans = {}
     work_schedules = {}
+    work_calendars = {}
+    work_times = {}
+    recurrence_patterns = {}
+    time_periods = {}
     tasks = {}
     task_times = {}
 
@@ -14,6 +18,9 @@ class Data:
         cls.work_plans = {}
         cls.work_schedules = {}
         cls.work_calendars = {}
+        cls.work_times = {}
+        cls.recurrence_patterns = {}
+        cls.time_periods = {}
         cls.tasks = {}
         cls.task_times = {}
 
@@ -25,6 +32,9 @@ class Data:
         cls.load_work_plans()
         cls.load_work_schedules()
         cls.load_work_calendars()
+        cls.load_work_times()
+        cls.load_recurrence_patterns()
+        cls.load_time_periods()
         cls.load_tasks()
         cls.load_task_times()
         cls.is_loaded = True
@@ -71,10 +81,37 @@ class Data:
         for work_calendar in cls._file.by_type("IfcWorkCalendar"):
             data = work_calendar.get_info()
             del data["OwnerHistory"]
-            del data["WorkingTimes"]
-            del data["ExceptionTimes"]
+            data["WorkingTimes"] = [t.id() for t in work_calendar.WorkingTimes or []]
+            data["ExceptionTimes"] = [t.id() for t in work_calendar.ExceptionTimes or []]
             cls.work_calendars[work_calendar.id()] = data
 
+    @classmethod
+    def load_work_times(cls):
+        cls.work_times = {}
+        for work_time in cls._file.by_type("IfcWorkTime"):
+            data = work_time.get_info()
+            data["Start"] = ifcopenshell.util.date.ifc2datetime(data["Start"]) if data["Start"] else None
+            data["Finish"] = ifcopenshell.util.date.ifc2datetime(data["Finish"]) if data["Finish"] else None
+            data["RecurrencePattern"] = work_time.RecurrencePattern.id() if work_time.RecurrencePattern else None
+            cls.work_times[work_time.id()] = data
+
+    @classmethod
+    def load_recurrence_patterns(cls):
+        cls.recurrence_patterns = {}
+        for recurrence_pattern in cls._file.by_type("IfcRecurrencePattern"):
+            data = recurrence_pattern.get_info()
+            data["TimePeriods"] = [t.id() for t in recurrence_pattern.TimePeriods or []]
+            cls.recurrence_patterns[recurrence_pattern.id()] = data
+
+    @classmethod
+    def load_time_periods(cls):
+        cls.time_periods = {}
+        for time_period in cls._file.by_type("IfcTimePeriod"):
+            cls.time_periods[time_period.id()] = {
+                "StartTime": ifcopenshell.util.date.ifc2datetime(time_period.StartTime),
+                "EndTime": ifcopenshell.util.date.ifc2datetime(time_period.EndTime),
+            }
+
     @classmethod
     def load_tasks(cls):
         cls.tasks = {}
diff --git a/src/ifcopenshell-python/ifcopenshell/api/sequence/edit_recurrence_pattern.py b/src/ifcopenshell-python/ifcopenshell/api/sequence/edit_recurrence_pattern.py
index ee57a173bc..f7691ad4e3 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/sequence/edit_recurrence_pattern.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/sequence/edit_recurrence_pattern.py
@@ -13,9 +13,14 @@ class Usecase:
             if name == "TimePeriods" and value:
                 periods = []
                 for period in value:
-                    periods.append(self.file.create_entity("IfcTimePeriod", **{
-                        "StartTime": ifcopenshell.util.date.datetime2ifc(period[0]),
-                        "EndTime": ifcopenshell.util.date.datetime2ifc(period[1])
-                    }))
+                    periods.append(
+                        self.file.create_entity(
+                            "IfcTimePeriod",
+                            **{
+                                "StartTime": ifcopenshell.util.date.datetime2ifc(period[0]),
+                                "EndTime": ifcopenshell.util.date.datetime2ifc(period[1]),
+                            },
+                        )
+                    )
                 value = periods
             setattr(self.settings["recurrence_pattern"], name, value)
diff --git a/src/ifcopenshell-python/ifcopenshell/api/sequence/edit_work_time.py b/src/ifcopenshell-python/ifcopenshell/api/sequence/edit_work_time.py
index 057cec6aba..c2952b704a 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/sequence/edit_work_time.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/sequence/edit_work_time.py
@@ -10,6 +10,6 @@ class Usecase:
 
     def execute(self):
         for name, value in self.settings["attributes"].items():
-            if name in ["Start", "Finish"]:
+            if value and name in ["Start", "Finish"]:
                 value = ifcopenshell.util.date.datetime2ifc(value, "IfcDate")
             setattr(self.settings["work_time"], name, value)
diff --git a/src/ifcopenshell-python/ifcopenshell/api/sequence/remove_time_period.py b/src/ifcopenshell-python/ifcopenshell/api/sequence/remove_time_period.py
new file mode 100644
index 0000000000..4b0d59d7aa
--- /dev/null
+++ b/src/ifcopenshell-python/ifcopenshell/api/sequence/remove_time_period.py
@@ -0,0 +1,12 @@
+import ifcopenshell.api
+
+
+class Usecase:
+    def __init__(self, file, **settings):
+        self.file = file
+        self.settings = {"time_period": None}
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        self.file.remove(self.settings["time_period"])
diff --git a/src/ifcopenshell-python/ifcopenshell/api/sequence/remove_work_calendar.py b/src/ifcopenshell-python/ifcopenshell/api/sequence/remove_work_calendar.py
index ee3c89327a..6950012bd9 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/sequence/remove_work_calendar.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/sequence/remove_work_calendar.py
@@ -1,3 +1,6 @@
+import ifcopenshell
+
+
 class Usecase:
     def __init__(self, file, **settings):
         self.file = file
diff --git a/src/ifcopenshell-python/ifcopenshell/api/sequence/remove_work_time.py b/src/ifcopenshell-python/ifcopenshell/api/sequence/remove_work_time.py
new file mode 100644
index 0000000000..10562c1840
--- /dev/null
+++ b/src/ifcopenshell-python/ifcopenshell/api/sequence/remove_work_time.py
@@ -0,0 +1,9 @@
+class Usecase:
+    def __init__(self, file, **settings):
+        self.file = file
+        self.settings = {"work_time": None}
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        self.file.remove(self.settings["work_time"])
diff --git a/src/ifcopenshell-python/ifcopenshell/api/sequence/unassign_recurrence_pattern.py b/src/ifcopenshell-python/ifcopenshell/api/sequence/unassign_recurrence_pattern.py
new file mode 100644
index 0000000000..23ec89376a
--- /dev/null
+++ b/src/ifcopenshell-python/ifcopenshell/api/sequence/unassign_recurrence_pattern.py
@@ -0,0 +1,12 @@
+import ifcopenshell.api
+
+
+class Usecase:
+    def __init__(self, file, **settings):
+        self.file = file
+        self.settings = {"recurrence_pattern": None}
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        self.file.remove(self.settings["recurrence_pattern"])
diff --git a/src/ifcopenshell-python/ifcopenshell/api/time/add_work_time.py b/src/ifcopenshell-python/ifcopenshell/api/time/add_work_time.py
deleted file mode 100644
index e69de29bb2..0000000000