EMZETT.Network Time
In short: A unified time synchronised over the network, which devices use to align their local clock.
In more detail: Usually implemented via the Network Time Protocol (NTP): devices periodically query specialised time servers and adjust their system clock accordingly. Correct, synchronised network time is important for, among other things, TLS certificate checking, log ordering, and time-based one-time passwords (TOTP/2FA).
In Depth
NTP works hierarchically in “stratum” levels: stratum-0 devices are highly precise reference clocks (atomic clocks, GPS receivers), stratum-1 servers are directly connected to them, stratum-2 servers synchronise with stratum-1 servers, and so on. Most end devices synchronise with public stratum-2 or stratum-3 servers (e.g. pool.ntp.org) and typically achieve millisecond-level accuracy.
Why accurate network time matters beyond mere convenience:
- TLS certificates have a validity window (issue and expiry date) — a system clock that’s significantly off can incorrectly reject valid certificates as expired or not yet valid.
- TOTP-based 2FA (e.g. authenticator apps) computes one-time codes from the current time — if a device’s clock is off by too much, the server and client codes no longer match.
- Logs and audit trails across several servers can only be put into the correct order if all involved systems use the same time base — otherwise it looks as if a later event happened before an earlier one.
See also: 2FA