fix(pkg/logfile): set creation date only if nil

pkg/logfile/logfile.go

@@ -176,6 +176,8 @@ func WriteTemperaturesCustom(temperatures []*types.Temperature, w io.Writer, com
 func writeCreationDate(temperatures []*types.Temperature) {
 	now := time.Now()
 	for _, temperature := range temperatures {
+		if temperature.CreationDate == nil {
 			temperature.CreationDate = &now
 		}
+	}
 }