This "not quite 5 minute guide to making an NTP server" is from 2014: https://ava.upuaut.net/?p=726 https://ava.upuaut.net/?p=726 So GPS boards for Raspberry P

This "not quite 5 minute guide to making an NTP server" is from 2014: https://ava.upuaut.net/?p=726 https://ava.upuaut.net/?p=726 So GPS boards for Raspberry Pi were cheap off-the-shelf hardware by 2014, at least.