ntpq -p reports all available servers have stratum 16. Therefor the time is cannot be set. However I can ping all the servers.

ntpq -p
     remote           refid      st t when poll reach   delay   offset  jitter
 master.stbuehle .INIT.          16 u    - 1024    0    0.000    0.000   0.000
 himalia.mysnip. .INIT.          16 u    - 1024    0    0.000    0.000   0.000
 x.ns.gin.ntt.ne .INIT.          16 u    - 1024    0    0.000    0.000   0.000
 services.freshd .INIT.          16 u    - 1024    0    0.000    0.000   0.000

the servers are:

server 0.debian.pool.ntp.org iburst
server 1.debian.pool.ntp.org iburst
server 2.debian.pool.ntp.org iburst
server 3.debian.pool.ntp.org iburst

Switching to different servers does not help either.

  • Do you have a firewall configured to block UDP port 123?
    – gbroiles
    Feb 2, 2017 at 9:12
  • 1
    This is normal for a stock installation of Raspbian. It only requires a little bit of editing to reach Stratum-1 servers. See my answer below:
    – SDsolar
    Jun 23, 2017 at 7:14

2 Answers 2


What you want is Stratum-1.

The only place for us to get that it by using time.nist.gov as your NTP server address.

The primary advantage of using that URL is because all the others have various response times and even downtimes. time.nist.gov is a "smart URL" which finds you the quickest and most accurate time from the National Bureau of Standards Master Clock. This is the same clock the Navy uses.

It is an easy change in Raspbian and most flavors of Ubuntu.

Rather than repeat what has already been written here about this, please allow me to refer you to a Q&A in this Stack Exchange that explains how to set it up:

How do I set Raspbian to use the primary time server time.nist.gov?

This article also mentions how to set your Windows computers to use the same Stratum-1 NTP source.

  • No, there are many stratum 1 servers on the internet, and overloading NIST is not a friendly thing to do. People should not do that.
    – Perry
    Jul 5, 2019 at 21:49

The Stratum 16 indication means that the clocks on those machines are misconfigured or otherwise not synchronized to NTP. It's a shame, but many servers in the ntp pool project seem to be desynchronized at this point. Don't worry about it too much; usually one gets a couple that are properly synchronized. Just "service ntp restart" if this happens and you'll get different servers.

(Don't use a specific host on the net like NIST's for synchronization unless you know it's okay to do so; you should almost always use the ntp pool.)

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