Public NTP/NTS Time Server
A time server in Ottawa, Canada, open to everyone.
Your local time:
Use this server
Pick the line that fits your device. With chrony, NTPsec or ntpd, add it to the configuration file and restart the time service.
Configuration line with NTS
server time.web-clock.ca iburst ntsFor chrony and NTPsec. Recommended, because your device can verify that the time really came from this server.
Configuration line without NTS
server time.web-clock.ca iburstFor chrony, NTPsec and ntpd where NTS is not available, for example an older version.
Windows, macOS and other devices
time.web-clock.caEnter this wherever Windows, macOS, a router or another device asks for an NTP server. Most of them do not support NTS.
What do these parameters mean? About the configuration lines.
iburst- With this option, your time software sends a quick burst of requests when it starts, so your clock settles faster.
nts- This option turns on Network Time Security, so the server is authenticated and your time packets are protected against tampering.
- Ports and firewall
- The time packets use UDP port 123, with or without NTS. NTS also uses TCP port 4460 for its key exchange. Make sure your firewall allows the ports you need outbound.
Live telemetry
Checking
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- Stratum
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- Receiver status
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- GNSS lock
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- UTC standard
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- Synchronised to
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- Satellites used
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- Typical offset (RMS)
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- Maximum error
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What do these parameters mean? About live telemetry.
- Status
- Whether chrony, the software that keeps the server’s time, is synchronised to a time source.
- Operating normally: chrony is synchronised to a source.
- Unsynchronised: chrony is not synchronised to any source.
- A dash: this page has no recent reading from the server, so it cannot say.
- Stratum
- How many steps away the server is from a real clock.
- 1: the server is synchronised directly to its satellite receiver, which is the normal state.
- A higher number: the server is using a network server instead, and is then one stratum higher than that server.
- A dash: the server is not synchronised.
- Receiver status
- What the satellite receiver itself reports about its fix.
- Timing: the receiver’s time mode. Its position was measured once, over a long survey, and is now fixed, so every satellite goes into the time instead of into working out where the receiver is. This gives the best time accuracy and is the normal state for this server.
- 3D fix: the receiver is still working out its position in three dimensions (including height) as well as the time, for example while a survey-in is running; the time is still accurate.
- 2D fix: the receiver can only work out a position without height, usually because too few satellites are usable, and the time is less accurate.
- No fix: the receiver has too few usable satellites to work out the time or a position, and chrony then normally switches to the backup time sources.
- Unknown: the receiver reported something the page does not recognise.
- + SBAS after the status: corrections from SBAS satellites (over North America, WAAS) are being applied.
- + DGPS after the status: corrections from another source are being applied.
- A dash: the receiver is not reporting.
- GNSS lock
- The satellite constellations the receiver is using right now.
- One or more names: GPS, Galileo, GLONASS, BeiDou or QZSS.
- A dash: the receiver is not using any.
- UTC standard
- Every satellite system keeps its own version of UTC, and national time laboratories keep their own too. This shows which version the server follows right now.
- UTC(USNO): the version kept by the United States Naval Observatory. GPS follows it, and so does QZSS, which always works together with GPS.
- UTC(SU): the version kept by Russia’s national time service, which GLONASS follows.
- UTC(NTSC): the version kept by the National Time Service Center of China, which BeiDou follows.
- UTC (European laboratories): the version kept jointly by several European time laboratories, which Galileo follows.
- Another UTC(…) name: the version kept by the national time laboratory behind the network server in use, for example UTC(NRC) for the National Research Council Canada.
- A dash: the server is following a source the page cannot name, or no source at all.
- Synchronised to
- The time source chrony is following right now.
- GNSS: the server’s own satellite receiver, which is the normal state.
- A server name: one of the backup servers listed under Time sources.
- A dash: the server is not synchronised.
- Satellites used
- How many satellites are feeding the receiver’s time, out of all those it can see.
- Satellites in view: the tile has this name, and shows only how many it can see, when the receiver does not say which ones it uses.
- A dash: the receiver is not reporting.
- Typical offset (RMS)
- The long-term average of how far the server’s clock was from its time source when chrony corrected it. Smaller is better. Nanoseconds (ns) are billionths of a second, microseconds (µs) millionths and milliseconds (ms) thousandths. A dash means the server is not synchronised.
- Maximum error
- chrony’s limit on how far the server’s clock could be from true time, assuming that the stratum 1 source at the start of the chain is correct. It is a cautious upper limit, so the real error is normally much smaller. A dash means the server is not synchronised.
Maximum error = |system time offset| + root dispersion + (0.5 × root delay)- |System time offset|: how far chrony estimates the clock is from true time at this moment, ignoring whether it is ahead or behind.
- Root dispersion: the uncertainty built up all the way back to the stratum 1 source.
- Root delay: the total network delay back to the stratum 1 source. Half of it counts, because the delay could lie entirely in one direction.
- Accuracy on your device
- These figures describe the server’s own clock against its time source, not the accuracy your device gets. That is mostly limited by the network path between your device and this server, which is usually far larger than these figures.
- Live updates
- The server refreshes these figures every minute, and this page reads them about once a minute while it is on screen. To save bandwidth, the page asks for nothing while it is in a background tab, and once it has been on screen for 8 hours it stops asking altogether. The clock at the top of the page goes blank, the status shows a dash, and the last figures stay on screen in grey. Select Resume live updates, or reload the page, to carry on. If the page has no recent reading from the server, every figure shows a dash.
Time sources
The server listens to its satellite receiver first and keeps these other sources as cross-checks and backups.
| Source | Type | Status | Stratum | UTC standard | Offset |
|---|
What do these parameters mean? About time sources.
- Source
- The name of the time source. The source chrony is synchronised to right now is highlighted. A number in brackets tells apart the servers of one pool, which share a name.
- Type
- What kind of source it is.
- Reference clock: a device attached to the server that measures time itself, here the satellite receiver.
- Network server: another time server reached over the internet.
- Peer: a server that exchanges time with this one in both directions. It appears only if the server is set up with one.
- Status
- Whether the source is answering, then chrony’s own verdict on it in brackets.
Online or Offline
- Online: the source answered at least one of the server’s last 8 requests.
- Offline: the source answered none of the server’s last 8 requests.
- Selected: the best source, which chrony is synchronised to right now.
- Combined: another source used for synchronisation, whose measurements chrony combines with the best source.
- Selectable: chrony considers the source fit for synchronisation, but is not using it at the moment.
- Falseticker: chrony thinks its time is wrong, because it disagrees with the other sources.
- Too variable: its time appears to vary too much for chrony to rely on it.
- Not selectable: chrony does not consider the source fit for synchronisation at the moment, for example because its replies do not pass chrony’s checks, it does not agree with a trusted source, or chrony does not have enough measurements of it yet.
- Green: selected or combined
- Grey: selectable or not selectable
- Amber: too variable
- Red: a falseticker, or a source that is offline
- Stratum
- The source’s own stratum.
- 0: the reference clock (it is the reference itself).
- 1: a network server connected directly to a reference clock.
- 2 or higher: a network server that takes its time from another network server, one stratum lower than itself.
- A dash: the source has not answered yet, so its stratum is not known.
- UTC standard
- The version of UTC that the source follows, whether or not the server is using that source right now.
- On the reference clock: the version the receiver follows, which depends on the satellite systems in use, in its fixed order of preference: GPS first, then GLONASS, BeiDou and Galileo.
- On a network server: the version kept by the national time laboratory behind that server.
- A dash: the version is not known, for example while the receiver has no fix.
- Offset
- How far the server’s clock is from that source, by chrony’s latest estimate. For a network server, the path across the internet adds some uncertainty, so differences of a fraction of a millisecond are normal.
- A plus sign: the server’s clock is ahead of the source.
- A minus sign: the server’s clock is behind the source.
- A dash: chrony has no measurement of that source yet.
UTC standards
| UTC standard | Laboratory | Country |
|---|
UTC (European laboratories) is not one laboratory’s standard. It is combined from several European time laboratories, and it is the version Galileo follows. It appears only if the receiver is using Galileo and no other satellite system.
UTC itself is calculated by the International Bureau of Weights and Measures (BIPM), from data contributed by about 80 time laboratories worldwide, using about 450 atomic clocks.
This is not a complete list of UTC standards, only those used by this server’s time sources.
About this server
The server is a Raspberry Pi 5 with 8 GB of RAM, and it is regularly monitored and maintained. Would you like to build your own? The setup guide walks through the whole process on a Raspberry Pi.
Satellite reference
u-blox NEO-M8T timing receiver
A u-blox NEO-M8T GNSS timing receiver, on a Waveshare timing HAT fitted to the Raspberry Pi, tracks navigation satellites and produces a precise one-pulse-per-second signal. The receiver sits at a fixed, surveyed-in position and runs in timing mode, which gives the best possible accuracy.
Pulse per second
Aligned to UTC
The receiver's one-pulse-per-second (PPS) output is aligned to UTC and wired to a GPIO pin on the Raspberry Pi, so the clock is locked to the pulse itself and not only to the time messages the receiver sends over its serial port. Live telemetry above shows which version of UTC the server is following.
Authenticated with NTS
NTS, RFC 8915
Network Time Security uses cryptographic authentication so that time responses cannot be altered or spoofed on their way to you. NTS is recommended over plain NTP wherever your client supports it.
Time protocols
NTPv4 and NTS
Standard NTPv4 works with practically any client, and NTS adds cryptographic authentication on top of it. The server responds to both NTPv4 and NTS requests, so you can use whichever your client supports.
Internet protocol
IPv4
The server is reachable over IPv4, at an address that can change from time to time. Please use the hostname rather than an IP address, so nothing breaks on your side if the address ever changes.
Backed up by national time laboratories
Automatic failover
If the satellite signals ever become unhealthy, the server switches to NTP and NTS servers that belong to national time laboratories. These official servers track various UTC standards using their own atomic clocks.
Service area
North America
The server is in Ottawa, Canada, and is intended for clients in North America, where the network delay to it is small. Delay is what limits accuracy, so clients elsewhere are usually better served by a closer server.
Uptime goal
Over 99%
The aim is to keep the server available more than 99% of the time. For the best reliability, configure your client with several servers, as RFC 8633 recommends (at least four independent sources), so it can keep time through any outage.
Software and services
chrony · gpsd · Let's Encrypt
The server uses chrony as its NTP and NTS server, with gpsd providing the interface to the GNSS receiver. The TLS certificate for this website is issued by Let's Encrypt, and chrony uses a copy of the same certificate to secure NTS connections.
Terms of use
Access
Free, no registration
The server is open to everyone, with NTP or NTS. Please use the hostname, not the IP address, which can change.
Fair use
Default polling, please
Please keep your time software's default polling settings, so your requests stay comfortably within the rate limits.
Firmware and software
Please ask first
Please don't hard-code this server into firmware or software distributions without written consent; just get in touch to ask.
Disclaimer
No warranty
This service is provided “as is”, without any warranty or guarantee of any kind. Use it at your own risk. See Legal & credits for the full details.