leapsecs.go | 16 ++++++++--------

diff --git a/leapsecs.go b/leapsecs.go
index e4d915244e5259f6117417add0c58e0fc77c2ea6874a8d7967644d5187ba63cb..d78d594f0ffde22b39fd61240bca91c7103ba578c7178278e9a5c700a9e37fa2 100644
--- a/leapsecs.go
+++ b/leapsecs.go
@@ -27,9 +27,9 @@ // Database of Unix timestamps of the time when leap second occurred.
 // Library contains and initializes it with leap seconds up to 2016-12-31.
 var Leapsecs LeapsecsList
 
-// Add leap seconds to the time (convert TAI to UTC).
-func (leapsecs LeapsecsList) Add(tai time.Time) (utc time.Time) {
-	orig := tai.Unix()
+// Add leap seconds to the time (convert UTC to TAI).
+func (leapsecs LeapsecsList) Add(utc time.Time) (tai time.Time) {
+	orig := utc.Unix()
 	v := orig
 	v += Leapsecs1972
 	for _, leapsec := range Leapsecs {
@@ -37,14 +37,14 @@ 		if v >= leapsec {
 			v++
 		}
 	}
-	utc = tai.Add(time.Second * time.Duration(v-orig))
+	tai = utc.Add(time.Second * time.Duration(v-orig))
 	return
 }
 
-// Subtract leap seconds from the time (convert UTC to TAI).
-func (leapsecs LeapsecsList) Sub(utc time.Time) (tai time.Time, isLeap bool) {
+// Subtract leap seconds from the time (convert TAI to UTC).
+func (leapsecs LeapsecsList) Sub(tai time.Time) (utc time.Time, isLeap bool) {
 	diff := int64(Leapsecs1972)
-	v := utc.Unix()
+	v := tai.Unix()
 	for _, leapsec := range leapsecs {
 		if v < leapsec {
 			break
@@ -55,7 +55,7 @@ 			isLeap = true
 			break
 		}
 	}
-	tai = utc.Add(-time.Second * time.Duration(diff))
+	utc = tai.Add(-time.Second * time.Duration(diff))
 	return
 }