diff --git a/utils/time.go b/utils/time.go
index 1531dc1..10e88a4 100644
--- a/utils/time.go
+++ b/utils/time.go
@@ -1,6 +1,8 @@
 package utils
 
-import "time"
+import (
+	"time"
+)
 
 func VeryBeginOfDate(date time.Time) time.Time {
 	return time.Date(date.Year(), date.Month(), date.Day(), 0, 0, 0, 0, date.Location())
@@ -10,7 +12,7 @@ func VeryEndOfDate(date time.Time) time.Time {
 	return time.Date(date.Year(), date.Month(), date.Day(), 23, 59, 59, 999999999, date.Location())
 }
 
-func IsNextMonth(t1, t2 time.Time) bool {
+func DifferenceInMonth(t1, t2 time.Time) int {
 	var differYear, differMonth int
 	if t1.After(t2) {
 		differYear = t1.Year() - t2.Year()
@@ -19,5 +21,9 @@ func IsNextMonth(t1, t2 time.Time) bool {
 		differYear = t2.Year() - t1.Year()
 		differMonth = int(t2.Month() - t1.Month())
 	}
-	return (differMonth == -11 && differYear == 1) || (differMonth == 1 && differYear == 0)
+	return differYear*12 + differMonth
+}
+
+func IsNextMonth(t1, t2 time.Time) bool {
+	return DifferenceInMonth(t1, t2) == 1
 }