Most current operating systems, including many small systems like IoT devices, use some form of NTP to sync time. NTP is lightweight and reasonably accurate in most use cases to synchronize time across the internet with millisecond accuracy [1]. Some protocols, like PTP, are more accurate but are designed for local networks and may require special hardware on the host [2]. Smaller systems with less stringent accuracy requirements sometimes use SNTP, a variant of NTP.
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