diff --git a/server/month.go b/server/month.go
index 4d46f3e..bd0c23d 100644
--- a/server/month.go
+++ b/server/month.go
@@ -22,6 +22,22 @@ func (m Month) FirstOfMonth() time.Time {
 	return time.Date(m.Year, time.Month(m.Month), 1, 0, 0, 0, 0, time.Now().Location())
 }
 
+func (m Month) Previous() Month {
+	if m.Month == 1 {
+		return Month{Year: m.Year - 1, Month: 12}
+	}
+
+	return Month{Year: m.Year, Month: m.Month - 1}
+}
+
+func (m Month) Next() Month {
+	if m.Month == 12 {
+		return Month{Year: m.Year + 1, Month: 1}
+	}
+
+	return Month{Year: m.Year, Month: m.Month + 1}
+}
+
 func (m Month) InFuture(date time.Time) bool {
 	if m.Year < date.Year() {
 		return true