added utc time functions

time.go

@@ -0,0 +1,22 @@
+package jwt
+
+import "time"
+
+// Now returns the current time in UTC Unix format
+func Now() int64 {
+	return NewNbf(time.Now())
+}
+
+// NewNbf returns a new 'not before' date
+func NewNbf(t time.Time) int64 {
+	return t.UTC().Unix()
+}
+
+// NewExp returns a new expiration date
+func NewExp(d time.Duration) int64 {
+	return newExp(time.Now(), d)
+}
+
+func newExp(t time.Time, d time.Duration) int64 {
+	return t.UTC().Add(d).Unix()
+}