diff --git a/cmd/kiwimix/config.go b/cmd/kiwimix/config.go
index 5d11ea5..3908717 100644
--- a/cmd/kiwimix/config.go
+++ b/cmd/kiwimix/config.go
@@ -12,7 +12,7 @@ import (
 )
 
 const (
-	programBinary string = "musala"
+	programBinary string = "kiwimix"
 )
 
 var (
diff --git a/go.mod b/go.mod
index d9649bf..85a7ac4 100644
--- a/go.mod
+++ b/go.mod
@@ -6,6 +6,12 @@ require (
 	github.com/PuloV/ics-golang v0.0.0-20190808201353-a3394d3bcade
 	github.com/spf13/cobra v1.7.0
 	github.com/spf13/viper v1.15.0
+	github.com/stretchr/testify v1.8.1
+)
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
 )
 
 require (
diff --git a/pkg/basetypes/calendar.go b/pkg/basetypes/calendar.go
index b26562c..c6d5344 100644
--- a/pkg/basetypes/calendar.go
+++ b/pkg/basetypes/calendar.go
@@ -14,19 +14,42 @@ func NewCalendar() *Calendar {
 	return &Calendar{*ics.NewCalendar()}
 }
 
-// SetEvent adds an event to the calendar
-func (cal *Calendar) SetEvent(event Event) (*Calendar, error) {
-	c, err := cal.SetEvent(event)
-	return c, err
+// ParseCalendarFile parses an ICS file and returns a calendar
+func ParseCalendarFile(filePath string) (*Calendar, error) {
+	return &Calendar{*ics.NewCalendar()}, nil
+}
+
+// AddEvent adds an event to the calendar
+func (cal *Calendar) AddEvent(event *Event) (*Calendar, error) {
+	//c, err := cal.SetEvent(event)
+	return cal, nil
+}
+
+// AddEvents adds all events to the calendar
+func (cal *Calendar) AddEvents(event []*Event) (*Calendar, error) {
+	//c, err := cal.SetEvent(event)
+	return cal, nil
+}
+
+// AddEvent adds an event to the calendar
+func (cal *Calendar) RemoveEvent(event *Event) (*Calendar, error) {
+	// c, err := cal.SetEvent(event)
+	return cal, nil
+}
+
+// AddEvent adds an event to the calendar
+func (cal *Calendar) RemoveEvents(event []*Event) (*Calendar, error) {
+	// c, err := cal.SetEvent(event)
+	return cal, nil
 }
 
 // GetEvents gets all events in the calendar
-func (cal *Calendar) GetEvents() []Event {
+func (cal *Calendar) GetEvents() []*Event {
 	subcal := cal.Calendar
 	subevents := subcal.GetEvents()
-	wrapped := make([]Event, len(subevents))
+	wrapped := make([]*Event, len(subevents))
 	for i, v := range subevents {
-		wrapped[i] = Event{v}
+		wrapped[i] = &Event{v}
 	}
 	return wrapped
 }
diff --git a/pkg/basetypes/calendar_test.go b/pkg/basetypes/calendar_test.go
new file mode 100644
index 0000000..e67f06e
--- /dev/null
+++ b/pkg/basetypes/calendar_test.go
@@ -0,0 +1,13 @@
+package basetypes_test
+
+import (
+	"testing"
+
+	"code.apps.glenux.net/glenux/kiwimix/pkg/basetypes"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCalendarFoo(t *testing.T) {
+	cal = basetypes.NewCalendar()
+	assert.Equal(t, cal, nil, "they should be equal")
+}
diff --git a/pkg/basetypes/event.go b/pkg/basetypes/event.go
index 7eb1ce9..edf7b9c 100644
--- a/pkg/basetypes/event.go
+++ b/pkg/basetypes/event.go
@@ -6,3 +6,7 @@ import ics "github.com/PuloV/ics-golang"
 type Event struct {
 	ics.Event
 }
+
+func (event *Event) Equals(other *Event) bool {
+	return false
+}
diff --git a/pkg/basetypes/stack.go b/pkg/basetypes/stack.go
index 5eec800..cccae11 100644
--- a/pkg/basetypes/stack.go
+++ b/pkg/basetypes/stack.go
@@ -1 +1,9 @@
 package basetypes
+
+type Stack struct {
+	calendars []Calendar
+}
+
+func (stack *Stack) Push(calendar *Calendar) (*Stack, error) {
+	return nil, nil
+}
diff --git a/pkg/calendarops/boolean_difference.go b/pkg/calendarops/boolean_difference.go
index 07f9f5c..85f2cef 100644
--- a/pkg/calendarops/boolean_difference.go
+++ b/pkg/calendarops/boolean_difference.go
@@ -13,10 +13,10 @@ type DifferenceCalendarOperation struct{}
 // Ensure DifferenceCalendarOperation implements CalendarOperation
 var _ CalendarOperation = (*DifferenceCalendarOperation)(nil)
 
-func (op DifferenceCalendarOperation) Execute(calendars ...basetypes.Calendar) (basetypes.Calendar, error) {
+func (op *DifferenceCalendarOperation) Execute(calendars ...*basetypes.Calendar) (*basetypes.Calendar, error) {
 	// Check that two calendars are provided
 	if len(calendars) != 2 {
-		return basetypes.Calendar{}, errors.New("difference operation requires exactly two calendars")
+		return &basetypes.Calendar{}, errors.New("difference operation requires exactly two calendars")
 	}
 
 	// Create a new calendar to store the difference
@@ -38,7 +38,7 @@ func (op DifferenceCalendarOperation) Execute(calendars ...basetypes.Calendar) (
 
 		// If the event is unique to the first calendar, add it to the difference calendar
 		if isUnique {
-			differenceCalendar.SetEvent(event1)
+			differenceCalendar.AddEvent(event1)
 		}
 	}
 
diff --git a/pkg/calendarops/boolean_intersect.go b/pkg/calendarops/boolean_intersect.go
index fa34c30..e9dde09 100644
--- a/pkg/calendarops/boolean_intersect.go
+++ b/pkg/calendarops/boolean_intersect.go
@@ -13,9 +13,9 @@ type IntersectCalendarOperation struct{}
 // Ensure IntersectCalendarOperation implements CalendarOperation
 var _ CalendarOperation = (*IntersectCalendarOperation)(nil)
 
-func (op IntersectCalendarOperation) Execute(calendars ...basetypes.Calendar) (basetypes.Calendar, error) {
+func (op *IntersectCalendarOperation) Execute(calendars ...*basetypes.Calendar) (*basetypes.Calendar, error) {
 	if len(calendars) != 2 {
-		return basetypes.Calendar{}, errors.New("Difference operation requires exactly two calendars")
+		return &basetypes.Calendar{}, errors.New("Difference operation requires exactly two calendars")
 	}
 	// Do your union operation here and return the new union basetypes.
 	return calendars[0], nil // Replace this with actual implementation
diff --git a/pkg/calendarops/boolean_union.go b/pkg/calendarops/boolean_union.go
index b45903c..31d853a 100644
--- a/pkg/calendarops/boolean_union.go
+++ b/pkg/calendarops/boolean_union.go
@@ -15,9 +15,9 @@ type UnionCalendarOperation struct {
 var _ CalendarOperation = (*UnionCalendarOperation)(nil)
 
 // Execute combines the events of two calendars and returns a new calendar that contains all events from both.
-func (op *UnionCalendarOperation) Execute(calendars ...basetypes.Calendar) (basetypes.Calendar, error) {
+func (op *UnionCalendarOperation) Execute(calendars ...*basetypes.Calendar) (*basetypes.Calendar, error) {
 	if len(calendars) != 2 {
-		return basetypes.Calendar{}, errors.New("Union operation requires exactly two calendars")
+		return &basetypes.Calendar{}, errors.New("Union operation requires exactly two calendars")
 	}
 	// Do your union operation here and return the new union basetypes.
 	return calendars[0], nil // Replace this with actual implementation
diff --git a/pkg/calendarops/calendar_operation.go b/pkg/calendarops/calendar_operation.go
index e7a442c..00466d4 100644
--- a/pkg/calendarops/calendar_operation.go
+++ b/pkg/calendarops/calendar_operation.go
@@ -4,5 +4,5 @@ import basetypes "code.apps.glenux.net/glenux/kiwimix/pkg/basetypes"
 
 // CalendarOperation defines the interface for operations on calendars.
 type CalendarOperation interface {
-	Execute(calendars ...basetypes.Calendar) (basetypes.Calendar, error)
+	Execute(calendars ...*basetypes.Calendar) (*basetypes.Calendar, error)
 }
diff --git a/pkg/calendarops/filter.go b/pkg/calendarops/filter.go
index 8c13021..c1b91a5 100644
--- a/pkg/calendarops/filter.go
+++ b/pkg/calendarops/filter.go
@@ -15,9 +15,9 @@ type FilterCalendarOperation struct {
 var _ CalendarOperation = (*FilterCalendarOperation)(nil)
 
 // Execute filters the events of a calendar and returns a new filtered calendar.
-func (op *FilterCalendarOperation) Execute(calendars ...basetypes.Calendar) (basetypes.Calendar, error) {
+func (op *FilterCalendarOperation) Execute(calendars ...*basetypes.Calendar) (*basetypes.Calendar, error) {
 	if len(calendars) != 1 {
-		return basetypes.Calendar{}, errors.New("Filter operation requires exactly one calendar")
+		return &basetypes.Calendar{}, errors.New("Filter operation requires exactly one calendar")
 	}
 	// Do your filter operation here and return the filtered calendar.
 	return calendars[0], nil // Replace this with actual implementation
diff --git a/pkg/calendarops/merge.go b/pkg/calendarops/merge.go
index 046bb3b..9bb6308 100644
--- a/pkg/calendarops/merge.go
+++ b/pkg/calendarops/merge.go
@@ -1,8 +1,6 @@
 package calendarops
 
 import (
-	"sort"
-
 	basetypes "code.apps.glenux.net/glenux/kiwimix/pkg/basetypes"
 )
 
@@ -19,27 +17,33 @@ func NewMergeCalendarOperation() *MergeCalendarOperation {
 }
 
 // Execute réalise l'opération de fusion.
-func (op *MergeCalendarOperation) Execute(cal ...basetypes.Calendar) (basetypes.Calendar, error) {
-	if len(cal.Events) == 0 {
-		return cal, nil
+func (op *MergeCalendarOperation) Execute(cal ...*basetypes.Calendar) (*basetypes.Calendar, error) {
+	// Guard: exit if no calendar provided
+	if len(cal) == 0 {
+		return nil, nil
 	}
 
-	sort.Slice(cal.Event, func(i, j int) bool {
-		return cal.Event[i].Start.Before(cal.Event[j].Start)
-	})
+	mergedEvents := cal[0].GetEvents()
+	/*
+		events := cal.GetEvents()
+		sort.Slice(cal.Event, func(i, j int) bool {
+			return cal.Event[i].Start.Before(cal.Event[j].Start)
+		})
 
-	mergedEvents := []basetypes.Event{cal.Event[0]}
+		mergedEvents := []basetypes.Event{cal.Event[0]}
 
-	for _, event := range cal.Event[1:] {
-		lastEvent := &mergedEvents[len(mergedEvents)-1]
-		if event.Start.Before(lastEvent.End) || event.Start.Equal(lastEvent.End) {
-			if event.End.After(lastEvent.End) {
-				lastEvent.End = event.End
+		for _, event := range cal.Event[1:] {
+			lastEvent := &mergedEvents[len(mergedEvents)-1]
+			if event.Start.Before(lastEvent.End) || event.Start.Equal(lastEvent.End) {
+				if event.End.After(lastEvent.End) {
+					lastEvent.End = event.End
+				}
+			} else {
+				mergedEvents = append(mergedEvents, event)
 			}
-		} else {
-			mergedEvents = append(mergedEvents, event)
 		}
-	}
-
-	return &basetypes.Calendar{Events: mergedEvents}, nil
+	*/
+	mergedCalendar := &basetypes.Calendar{}
+	mergedCalendar.AddEvents(mergedEvents)
+	return mergedCalendar, nil
 }
diff --git a/pkg/stackops/generate.go b/pkg/stackops/generate.go
index 9977f5b..ad8fa6f 100644
--- a/pkg/stackops/generate.go
+++ b/pkg/stackops/generate.go
@@ -1,16 +1,24 @@
 package stackops
 
-import "time"
+import (
+	"time"
+
+	basetypes "code.apps.glenux.net/glenux/kiwimix/pkg/basetypes"
+)
 
 // GeneratorLimit is a type definining
 type GenerateConfig struct {
-	DateBegin *time.Date
-	DateEnd   *time.Date
+	DateBegin *time.Time
+	DateEnd   *time.Time
 	TimeBegin *time.Time
 	TimeEnd   *time.Time
 }
 
+type GenerateStackOperation struct{}
+
+var _ StackOperation = (*GenerateStackOperation)(nil)
+
 // generate events that last all day (from X hour to Y hour)
-func (cal *Calendar) generate() *Calendar {
-	return nil
+func (op *GenerateStackOperation) Execute(stack *basetypes.Stack, str string) (*basetypes.Stack, error) {
+	return nil, nil
 }
diff --git a/pkg/stackops/load.go b/pkg/stackops/load.go
index 7365e72..8b27809 100644
--- a/pkg/stackops/load.go
+++ b/pkg/stackops/load.go
@@ -6,8 +6,8 @@ import (
 
 type LoadOperation struct{}
 
-func (op *LoadOperation) Execute(stack *basetypes.CalendarStack, filePath string) error {
-	cal, err := basetypes.ParseICSFile(filePath) // hypothetically, ParseICSFile parses an ICS file into a Calendar object
+func (op *LoadOperation) Execute(stack *basetypes.Stack, filePath string) error {
+	cal, err := basetypes.ParseCalendarFile(filePath) // hypothetically, ParseICSFile parses an ICS file into a Calendar object
 	if err != nil {
 		return err
 	}
diff --git a/pkg/stackops/save.go b/pkg/stackops/save.go
index 7215c31..732386c 100644
--- a/pkg/stackops/save.go
+++ b/pkg/stackops/save.go
@@ -13,7 +13,7 @@ func NewSaveOperation(filePath string) *SaveOperation {
 	return saveop
 }
 
-func (op *SaveOperation) Execute(stack *basetypes.CalendarStack) error {
+func (op *SaveOperation) Execute(stack *basetypes.Stack) error {
 	cal, err := basetypes.ParseCalendarFile(op.filePath)
 	if err != nil {
 		return err
diff --git a/pkg/stackops/stack_operation.go b/pkg/stackops/stack_operation.go
index f5d6663..1ba4b30 100644
--- a/pkg/stackops/stack_operation.go
+++ b/pkg/stackops/stack_operation.go
@@ -1,5 +1,7 @@
 package stackops
 
+import basetypes "code.apps.glenux.net/glenux/kiwimix/pkg/basetypes"
+
 type StackOperation interface {
-	Execute(stack *CalendarStack, filePath string) error
+	Execute(stack *basetypes.Stack, filePath string) (*basetypes.Stack, error)
 }