Yesterday, Chinese security services published a story alleging a multi-year attack against the systems operating the Chinese standard time (CST), sometimes called Beijing Standard Time. China uses only one time zone across the country, and has not used daylight saving time since 1991. Most operating systems use UTC internally and display local time zones for user convenience. Modern operating systems use NTP to synchronize time. Popular implementations are ntpd and chrony. The client will poll several servers, disregard outliers, and usually sync with the "best" time server based on latency and jitter detected.