learned I didn't need git for external modules and different folders can have different mains

pkg/date/date.go

@@ -0,0 +1,56 @@
+package calendar
+
+import "errors"
+
+// Date Struct
+type Date struct {
+	year  int
+	month int
+	day   int
+}
+
+// Setter Methods
+
+// SetYear Method
+func (d *Date) SetYear(year int) error {
+	if year < 1 {
+		return errors.New("invalid year")
+	}
+	d.year = year
+	return nil
+}
+
+// SetMonth Method
+func (d *Date) SetMonth(month int) error {
+	if month < 1 || month > 12 {
+		return errors.New("invalid month")
+	}
+	d.month = month
+	return nil
+}
+
+// SetDay Method
+func (d *Date) SetDay(day int) error {
+	if day < 1 || day > 31 {
+		return errors.New("invalid day")
+	}
+	d.day = day
+	return nil
+}
+
+// Getter Methods
+
+// Year Method
+func (d *Date) Year() int {
+	return d.year
+}
+
+// Month Method
+func (d *Date) Month() int {
+	return d.month
+}
+
+// Day Method
+func (d *Date) Day() int {
+	return d.day
+}

pkg/date/event.go

@@ -0,0 +1,23 @@
+package calendar
+
+import (
+	"errors"
+	"unicode/utf8"
+)
+
+type Event struct {
+	title string
+	Date
+}
+
+func (e *Event) Title() string {
+	return e.title
+}
+
+func (e *Event) SetTitle(title string) error {
+	if utf8.RuneCountInString(title) > 32 {
+		return errors.New("invalid title length")
+	}
+	e.title = title
+	return nil
+}