At least for Europe, it is accurate. Frequency is actively changed to maintain 50Hz in long term: https://www.mainsfrequency.com/gridtime.php https://www.mainsf

At least for Europe, it is accurate. Frequency is actively changed to maintain 50Hz in long term: https://www.mainsfrequency.com/gridtime.php https://www.mainsfrequency.com/gridtime.php