added helper function, and fixed #28

Backend/helper/time.go

@@ -20,6 +20,11 @@ func IsWeekend(ts time.Time) bool {
 	return ts.Weekday() == time.Saturday || ts.Weekday() == time.Sunday
 }
 
+func GetKW(t time.Time) int {
+	_, kw := t.ISOWeek()
+	return kw
+}
+
 // Converts duration to string
 func FormatDuration(d time.Duration) string {
 	hours := int(d.Abs().Hours())