The Physikalisch-Technische Bundesanstalt (PTB), Germany’s national metrology institute, operates three public NTP servers synchronized directly to its atomic clocks.
PTB’s servers are a reference-grade source for users in Germany and beyond, and they support NTS (Network Time Security) for cryptographically authenticated time.
| Hostname | Note |
|---|---|
ptbtime1.ptb.de
| Braunschweig, stratum 1 |
ptbtime2.ptb.de
| Braunschweig, stratum 1 |
ptbtime3.ptb.de
| Braunschweig, stratum 1 |
Supports NTS via TCP port 4460 (NTS-KE). Example chrony line: server ptbtime1.ptb.de iburst nts