iTechGuides is reader-supported. When you buy through links on our site, we may earn an affiliate commission. As an Amazon Associate I earn from qualifying purchases. Learn more
GPS time is not UTC, and NTP cannot correct a leap second safely unless the system knows which time scale it is receiving and which leap-second policy it follows. A GPS receiver supplies a highly stable reference, often with a pulse-per-second (PPS) signal. NTP then distributes a UTC interpretation of that reference through a hierarchy of servers and clients. Leap-second announcements, compatible software, and consistent handling of smeared or unsmeared time are what prevent an accurate clock from producing an incorrect timestamp.
GPS time, UTC and NTP are different parts of the chain
UTC is the civil time scale used by national laboratories and public time services. It is based on atomic time but is adjusted with leap seconds so that civil time remains close to the irregular rotation of Earth. GPS maintains its own continuous time scale instead of inserting leap seconds whenever UTC does.
The Network Time Foundation’s The NTP Timescale and Leap Seconds reference, updated October 2, 2026, describes GPS as syntonic with International Atomic Time (TAI) but fixed at 19 seconds behind TAI. Its wording is: “The GPS timescale is syntonic with TAI, but at a fixed time offset of -19 s from TAI, apparently because the final system design review was in 1980.” A receiver therefore cannot simply copy its displayed GPS count into a field labelled UTC. It must apply the current and historical leap-second relationship before presenting civil time.
Free tools Windows power users keep installed
One-click scans. No signup required.
NTP (Network Time Protocol) is the distribution layer. A primary NTP server obtains time from a reference clock, then serves secondary servers and end-user systems over a network. A workstation generally does not need its own antenna or satellite receiver; it needs a trustworthy upstream server and a local daemon that can discipline its clock.
#1 Best Overall
- Read Before You Buy — No Video Output: These adapters support charging and USB 2.0 data transfer, but cannot transmit video signals. Except for standard USB webcams (which use USB data only), they are not compatible with HDMI/DisplayPort cables, video-capable USB-C hubs, or docking stations with video output.
- Convert USB-A Ports to USB-C: Designed to connect USB-C earphones, cables, flash drives, card readers, and other USB-C accessories to standard USB-A ports. Plug-and-play with no drivers or software required.
- Aluminum Alloy Housing: Built with a sturdy aluminum alloy shell that aids in heat dissipation and protects against daily wear and scratches. Designed to maintain a stable and secure connection.
- Compact & Travel-Friendly: The ultra-compact design allows the adapter to stay plugged into your device without blocking adjacent ports or adding bulk, reducing wear and tear on your original USB ports.
- 12-Month Warranty: Backed by a 12-month manufacturer warranty for peace of mind. Designed to meet strict quality control standards for reliable everyday performance.
What a GPS timing receiver contributes
- A continuous timing reference derived from the satellite system.
- A time-of-day message that identifies the receiver’s interpretation of the current time scale.
- Often a PPS output, an electrical pulse marking the start of each second. PPS can give a local server a precise interval reference when the operating system, interface and driver support it.
The receiver’s data and PPS signal are inputs, not a complete leap-second policy. Reference-clock software must know how to interpret the messages, obtain leap information and convert GPS time to UTC when that is what downstream systems expect.
How NTP distributes that interpretation
- A reference source, such as a GPS receiver, provides timing data to a primary server.
- The primary server associates that source with UTC and advertises its status and leap information in NTP.
- Secondary servers select one or more upstream sources, compare samples and discipline their own clocks.
- Clients query the secondary or primary servers and gradually correct their local clocks rather than relying on a one-time manual setting.
This hierarchy means that the quality of a client’s time depends on the entire synchronization chain: source conversion, leap data, network paths, server selection, daemon behavior and the local operating-system clock.
What a leap second changes
A leap second changes the mapping between UTC clock readings and elapsed atomic time. It does not change the physical frequency of a computer’s quartz oscillator or the satellite signal’s underlying frequency. At the event, UTC includes an additional second (or, in a future policy, could omit one); software must decide how to represent that change in the system clock.
Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Scan for outdated or missing drivers - takes under a minute3Repair Windows errors before they cause bigger problemsThe NTP 4.2.8 documentation says a daemon can learn about a pending leap through IERS bulletins, national time-and-frequency signals, GPS signals, NTP packets or a leap-seconds file. A reference clock may pass the information to a primary server, which can propagate it through the NTP subnet. Support is driver-dependent, so the presence of a GPS receiver does not prove that the host is receiving or applying its leap indication.
Rank #2
- 5-in-1 USB-C Hub: Experience comprehensive connectivity featuring a Power Delivery input, two USB-A 2.0 ports, a USB-A 3.0 port, and an HDMI port. (Note: The USB-C power delivery input port is only for connecting an external wall charger to power your laptop and cannot power peripheral devices.)
- 90W Pass-Through Charging: Achieve optimal charging with 90W pass-through power to your laptop, supported by a total input of 100W, with the hub reserving 10W for operational efficiency. (Note: Wall charger not included.)
- Quick Data Transfers: Accelerate your productivity with rapid data transfers using a high-speed 5Gbps USB 3.0 port and two 480Mbps USB 2.0 ports.
- 4K HDMI Display: Enhance your visual experience with a hub capable of delivering 4K resolution at 30Hz in both mirror and extend modes. Please note that this hub is compatible with MacBook (macOS 12 and newer), Windows 10 and 11, ChromeOS, and laptops equipped with DP Alt Mode and Power Delivery. Note: This device is not compatible with Linux.
- What You Get: Anker USB-C Hub (5-in-1, 4K HDMI), welcome guide, 18-month warranty, and our friendly customer service.
Advance notice is essential
Leap processing is safest when the system knows in advance that a leap is pending. The daemon can then arm the kernel or schedule its selected correction at the proper UTC boundary. If the upstream source, driver, daemon and kernel disagree about the announcement, one server can step or repeat a second while another continues on a different time policy.
Kernel-assisted handling and fallback behavior
Where precision-time kernel support is available and enabled, the NTP documentation describes arming the kernel to apply the leap at the end of the day. Without that support, the documented fallback adjusts the clock so that a second is effectively repeated or stalled. These are implementation details, not universal promises: behavior depends on the NTP release, operating system, kernel configuration and clock driver. The NTP implementation guidance used here concerns the 4.2.8 series and was last updated November 23, 2022.
Leap smear versus direct UTC handling
There are two broad operational policies for representing a leap:
Quick wins for a faster PC:
Clear out junk files and repair common Windows errorsFree Scan →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Repair Windows errors before they cause bigger problemsFix Now →| Policy | What the clock does | When it fits | Main risk |
|---|---|---|---|
| Direct UTC (step or repeat) | Represents the leap at the UTC event, using kernel support or the documented repeated-second fallback. | Systems whose logs, protocols or legal records must follow UTC directly. | Applications that assume every day has exactly 86,400 seconds may mishandle the event. |
| Leap smear | Spreads the adjustment over a configured window so the clock changes gradually. | Controlled fleets that can use the same smear schedule and need to avoid an abrupt clock discontinuity. | During the window, the clock temporarily diverges from unsmeared UTC. |
The NTP leap-smear REFID proposal describes indicating in a packet that the time already contains smear correction. A smeared clock is not simply “wrong”; it follows a different time policy during the interval. The failure occurs when one system writes a smeared timestamp and another interprets it as unsmeared UTC, or when servers with different smear windows exchange measurements without accounting for the offset.
Rank #3
- Sleek 7-in-1 USB-C Hub: Features an HDMI port, two USB-A 3.0 ports, and a USB-C data port, each providing 5Gbps transfer speeds. It also includes a USB-C PD input port for charging up to 100W and dual SD and TF card slots, all in a compact design.
- Flawless 4K@60Hz Video with HDMI: Delivers exceptional clarity and smoothness with its 4K@60Hz HDMI port, making it ideal for high-definition presentations and entertainment. (Note: Only the HDMI port supports video projection; the USB-C port is for data transfer only.)
- Double Up on Efficiency: The two USB-A 3.0 ports and a USB-C port support a fast 5Gbps data rate, significantly boosting your transfer speeds and improving productivity.
- Fast and Reliable 85W Charging: Offers high-capacity, speedy charging for laptops up to 85W, so you spend less time tethered to an outlet and more time being productive.
- What You Get: Anker USB-C Hub (7-in-1), welcome guide, 18-month warranty, and our friendly customer service.
Keep a fleet on one policy
- Document whether each tier uses direct UTC or a smear.
- Use upstream servers whose policy matches the clients they serve.
- Do not mix a smeared source with an unsmeared source in the same selection pool unless the software explicitly identifies and handles the difference.
- Record the policy with exported timestamps, especially for distributed logs, financial events and telemetry.
How to configure a normal workstation or server safely
Most systems should use a maintained NTP service rather than attach a satellite receiver directly. The exact command names and configuration files vary by operating system and daemon, so verify the documentation for the software installed on the host.
- Choose a maintained NTP implementation. Install security and timekeeping updates. The NTP 4.2.8 material documents mechanisms, but does not establish identical behavior for every current operating system or derivative daemon.
- Configure more than one trusted upstream source. Multiple sources let the daemon detect an outlier and continue if one path fails. Ensure the sources agree on leap policy.
- Verify leap information. Confirm that the daemon can receive leap status through NTP, a reference-clock signal or a current leap-seconds file. A stale file can leave an otherwise synchronized clock with the wrong UTC interpretation.
- Check kernel and daemon support. Determine whether precision-time kernel handling is enabled and which fallback the daemon uses when it is not.
- Observe, do not just set. Monitor source selection, offset, stratum, reachability and leap status. A displayed “synchronized” state does not prove that a leap announcement was received.
- Test policy compatibility. Before a scheduled leap, identify services that exchange timestamps across administrative boundaries and verify whether they expect smeared or unsmeared time.
Building a local NTP server with GPS
A local GPS reference is useful when a site needs independence from upstream network time or has a private timing hierarchy. The basic design is a receiver connected to a server, with the receiver’s time-of-day data and, where possible, PPS supplied to a compatible reference-clock driver.
Check these requirements before buying hardware
- PPS interface: confirm that the receiver exposes PPS in a form your operating system and interface hardware can timestamp.
- Driver support: verify that your NTP daemon has a driver for the receiver’s protocol and can combine message data with PPS.
- Leap notification: establish how the receiver reports pending leap information and whether the driver passes it to NTP.
- Antenna installation: provide a suitable sky view, cable length and power arrangement; satellite visibility alone does not guarantee correct leap processing.
- Holdover behavior: decide what the server should do if the antenna, receiver or network input fails.
The documented sources support GPS plus PPS as a timing-source category, but they do not test current receiver models, antennas or accuracy figures. Choose against the interface and software requirements rather than an unverified product specification.
Recommended Free Tools
Use a hierarchy, not a single point of failure
A GPS-backed primary server can feed several secondary servers. Give those secondaries independent network paths and, where practical, another reference source. Clients should normally use the secondary tier. This limits the blast radius of a receiver failure and makes it easier to compare sources before accepting a correction.
Rank #4
- Dual Converters, Infinite Potential：Includes 2× USB C male to USB A female adapters and 2× USB A male to USB C female adapters. Perfect for a wide range of uses—tablets with Bluetooth keyboards, expand USB ports on macbook, and more. Two different converters for all your daily needs
- Next-Level 10Gbps & 3A Charging: No more slow 480Mbps, this usb to usb c adapter has a transfer speed of up to 10Gbps, allowing you to do more transferring in less time. This usb adapter fits both USB A and USB C charger, supporting up to 3A fast charging
- Upgraded Exquisite Craftsmanship: With an aluminum alloy housing and metal connector, the usbc to usb adapter is extremely durable and sturdy. Rigorously tested to withstand more than 10,000 times of plugging and unplugging, ensuring long-lasting performance
- Broad Compatible: The usb c to usb adapter widely supports all USB C/ USB A devices like laptops, tablets, cellphones, car chargers, and phone chargers. Such as compatible with MacBook Pro/Air 2023/2022, Thunderbolt 4/3 Devices,Apple MagSafe Watch 9/8/7/SE/Ultra, iPad Pro 2022/2021, Samsung Galaxy S23/S20/S10, and iPhone 17/16/15 Pro. Plug and play
- Please Note: To reach 10Gbps speed, keep the cable under 3.3 ft. For USB A Male to USB C adapters, try flipping the USB C connector. USB C Male to USB A adapters support bidirectional 10Gbps transfer within 3.3 ft
Why a synchronized clock can still produce a bad timestamp
Synchronization answers “what time does this clock represent now?” It does not automatically answer “what time scale did this historical record use?” A timestamp written before or during a leap may need the leap-second history that was applicable to that epoch. The NTP timescale reference warns that historic epochs can be misinterpreted if later leap-second information is not applied.
Questions to ask when converting historical data
- Was the original value labelled UTC, GPS time, TAI, Unix time or only a local wall-clock string?
- Did the producing system use direct UTC or a leap smear?
- Which leap-second table and software version performed the conversion?
- Does the format represent an inserted second unambiguously, or can two events share the same displayed second?
- Are source and destination systems using the same historical leap records?
A present-day GPS-to-UTC offset is not enough to reconstruct every past relationship. The number of UTC leap adjustments between the event and the conversion date matters.
Choosing between network NTP and local GPS
| Decision factor | Network NTP | Local GPS reference |
|---|---|---|
| Dependency | Requires reachable, trusted upstream servers. | Can provide an independent local reference, but depends on receiver, antenna, power and driver. |
| Deployment effort | Usually lower; configure the daemon and monitor the network path. | Higher; install hardware, antenna, PPS interface and compatible software. |
| Leap handling | Relies on upstream servers and local daemon support for leap announcements. | Still requires correct GPS-to-UTC conversion and driver support for leap notification. |
| Best fit | General workstations and servers with reliable network access. | Sites needing local independence or a primary timing source for an internal hierarchy. |
Neither choice removes the need for a leap-second policy. A GPS signal is a reference; NTP is a distribution protocol; UTC interpretation and leap processing remain software and configuration responsibilities.
Common failure modes and recovery steps
The clock is close to GPS but wrong by a whole number of seconds
Check whether the receiver’s output is GPS time rather than UTC, and whether the driver has current leap information. Do not “fix” the display by manually subtracting a guessed offset; update the conversion and verify the source’s advertised leap status.
Best Value
- 5-in-1 Connectivity: Equipped with a 4K HDMI port, a 5 Gbps USB-C data port, two 5 Gbps USB-A ports, and a USB C 100W PD-IN port. Note: The USB C 100W PD-IN port supports only charging and does not support data transfer devices such as headphones or speakers.
- Powerful Pass-Through Charging: Supports up to 85W pass-through charging so you can power up your laptop while you use the hub. Note: Pass-through charging requires a charger (not included). Note: To achieve full power for iPad, we recommend using a 45W wall charger.
- Transfer Files in Seconds: Move files to and from your laptop at speeds of up to 5 Gbps via the USB-C and USB-A data ports. Note: The USB C 5Gbps Data port does not support video output.
- HD Display: Connect to the HDMI port to stream or mirror content to an external monitor in resolutions of up to 4K@30Hz. Note: The USB-C ports do not support video output.
- What You Get: Anker 332 USB-C Hub (5-in-1), welcome guide, our worry-free 18-month warranty, and friendly customer service.
Servers disagree around the leap event
Compare their upstream sources and smear settings. Remove or isolate sources following a different policy, refresh leap data and confirm kernel support. If the fleet requires direct UTC, ensure every tier is configured for direct handling rather than mixing in a smear.
The daemon reports synchronization but historical logs do not line up
Identify the timestamp scale and leap table used when each record was created. Reprocess the conversion with the appropriate historical leap-second history instead of applying today’s offset to every record.
PPS is present but the result is unstable
Verify PPS electrical capture, driver selection, timestamping support and whether the time-of-day message is being paired with the correct pulse. PPS improves the interval reference only when the complete software and hardware path interprets it correctly.
How often do leap seconds occur?
The Network Time Foundation reference uses roughly eighteen months as historical context for the interval between leap seconds while explaining that actual intervals vary. It is not a schedule or a prediction. Administrators should wait for an authoritative announcement and update their leap information rather than planning from an average.
Operational checklist
- Label every time source as GPS, UTC, TAI, smeared UTC or another defined scale.
- Keep the daemon, operating system and leap-second data maintained.
- Confirm that reference-clock drivers pass leap notifications.
- Document whether the fleet uses direct UTC or a smear, including the smear window if applicable.
- Monitor source reachability, offset, stratum and leap status.
- Preserve time-scale metadata with long-lived logs and datasets.
- Review behavior for the specific NTP version, kernel and driver in use; implementations are not interchangeable.
Bottom line
GPS and NTP avoid leap-second errors by performing different jobs correctly. GPS supplies a continuous reference that is not UTC. NTP distributes a UTC interpretation through a server hierarchy. Leap announcements and historical tables tell software when and how UTC changes, while a consistent direct-UTC or leap-smear policy keeps cooperating systems aligned. Treat the reference source, conversion rules, protocol behavior and timestamp format as one chain; a strong signal alone cannot guarantee a correct civil-time record.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
