Just implement update logic in Methods where it is needed, since if there is no pointer I cannot hand it to any function or method

feed.go

@@ -38,7 +38,12 @@ func NewFeed(title string) *Feed {
 // AddAuthor adds the Person as an author to the Feed. It returns its index as
 // an int.
 func (f *Feed) AddAuthor(p *Person) int {
-	f.Updated.Update()
+	if f.Updated == nil {
+		f.Updated = NewDate(time.Now())
+	} else {
+		f.Updated.DateTime = DateTime(time.Now())
+	}
+
 	return addToSlice(&f.Authors, p)
 }
 
@@ -48,13 +53,23 @@ func (f *Feed) DeleteAuthor(index int) error {
 		return fmt.Errorf("error deleting author %v from entry %v: %v", index, f.ID.URI, err)
 	}
 
-	f.Updated.Update()
+	if f.Updated == nil {
+		f.Updated = NewDate(time.Now())
+	} else {
+		f.Updated.DateTime = DateTime(time.Now())
+	}
+
 	return nil
 }
 
 // AddCategory adds the Category to the Feed. It returns its index as an int.
 func (f *Feed) AddCategory(c *Category) int {
-	f.Updated.Update()
+	if f.Updated == nil {
+		f.Updated = NewDate(time.Now())
+	} else {
+		f.Updated.DateTime = DateTime(time.Now())
+	}
+
 	return addToSlice(&f.Categories, c)
 }
 
@@ -65,14 +80,24 @@ func (f *Feed) DeleteCategory(index int) error {
 		return fmt.Errorf("error deleting category %v from entry %v: %v", index, f.ID.URI, err)
 	}
 
-	f.Updated.Update()
+	if f.Updated == nil {
+		f.Updated = NewDate(time.Now())
+	} else {
+		f.Updated.DateTime = DateTime(time.Now())
+	}
+
 	return nil
 }
 
 // AddContributor adds the Person as a contributor to the Feed. It returns its
 // index as an int.
 func (f *Feed) AddContributor(c *Person) int {
-	f.Updated.Update()
+	if f.Updated == nil {
+		f.Updated = NewDate(time.Now())
+	} else {
+		f.Updated.DateTime = DateTime(time.Now())
+	}
+
 	return addToSlice(&f.Contributors, c)
 }
 
@@ -83,14 +108,24 @@ func (f *Feed) DeleteContributor(index int) error {
 		return fmt.Errorf("error deleting contributor %v from entry %v: %v", index, f.ID.URI, err)
 	}
 
-	f.Updated.Update()
+	if f.Updated == nil {
+		f.Updated = NewDate(time.Now())
+	} else {
+		f.Updated.DateTime = DateTime(time.Now())
+	}
+
 	return nil
 }
 
 // AddLink adds the Link to the Feed. There should be one Link with Rel "self".
 // It returns its index as an int.
 func (f *Feed) AddLink(l *Link) int {
-	f.Updated.Update()
+	if f.Updated == nil {
+		f.Updated = NewDate(time.Now())
+	} else {
+		f.Updated.DateTime = DateTime(time.Now())
+	}
+
 	return addToSlice(&f.Links, l)
 }
 
@@ -100,13 +135,23 @@ func (f *Feed) DeleteLink(index int) error {
 		return fmt.Errorf("error deleting link %v from entry %v: %v", index, f.ID.URI, err)
 	}
 
-	f.Updated.Update()
+	if f.Updated == nil {
+		f.Updated = NewDate(time.Now())
+	} else {
+		f.Updated.DateTime = DateTime(time.Now())
+	}
+
 	return nil
 }
 
 // AddExtension adds the Extension to the Feed. It returns its index as an int.
 func (f *Feed) AddExtension(e *ExtensionElement) int {
-	f.Updated.Update()
+	if f.Updated == nil {
+		f.Updated = NewDate(time.Now())
+	} else {
+		f.Updated.DateTime = DateTime(time.Now())
+	}
+
 	return addToSlice(&f.Extensions, e)
 }
 
@@ -117,13 +162,23 @@ func (f *Feed) DeleteExtension(index int) error {
 		return fmt.Errorf("error deleting extension %v from entry %v: %v", index, f.ID.URI, err)
 	}
 
-	f.Updated.Update()
+	if f.Updated == nil {
+		f.Updated = NewDate(time.Now())
+	} else {
+		f.Updated.DateTime = DateTime(time.Now())
+	}
+
 	return nil
 }
 
 // AddEntry adds the Entry to the Feed. It returns its index as an int.
 func (f *Feed) AddEntry(e *Entry) int {
-	f.Updated.Update()
+	if f.Updated == nil {
+		f.Updated = NewDate(time.Now())
+	} else {
+		f.Updated.DateTime = DateTime(time.Now())
+	}
+
 	return addToSlice(&f.Entries, e)
 }
 
@@ -133,7 +188,12 @@ func (f *Feed) DeleteEntry(index int) error {
 		return fmt.Errorf("error deleting entry %v from entry %v: %v", index, f.ID.URI, err)
 	}
 
-	f.Updated.Update()
+	if f.Updated == nil {
+		f.Updated = NewDate(time.Now())
+	} else {
+		f.Updated.DateTime = DateTime(time.Now())
+	}
+
 	return nil
 }
 
@@ -155,7 +215,12 @@ func (f *Feed) DeleteEntryByURI(uri string) error {
 	}
 
 	f.Entries = append(f.Entries[:index], f.Entries[index+1:]...)
-	f.Updated.Update()
+	if f.Updated == nil {
+		f.Updated = NewDate(time.Now())
+	} else {
+		f.Updated.DateTime = DateTime(time.Now())
+	}
+
 	return nil
 }