TrueOffset vs Prime Time NTP

TrueOffset measures how far your iPhone or iPad's clock is from the world's time servers, and which way. Compare Network Time Protocol (NTP) servers with one another, see how far apart they are, and set any of them as your reference. FIVE CLOCK FACES - 12-Hour Classic — Traditional analog display - 24-Hour Scientific — Full day on one dial - NTP Offset — Dual second hands show device vs. true time - Digital — Large display with millisecond precision - Time Code — A radio time code spelled out second by second UTC & TAI TIME SCALES Show Coordinated Universal Time (UTC) and International Atomic Time (TAI), 37 seconds ahead of it, beside your local time, with deadbeat second hands that step on each second. TIME SIGNALS Hear the true second. Optional pips are timed against your NTP reference, so the start of each one marks the real second, not your device's idea of it. Choose from the classic broadcast signals, synthesized to their published pitch and timing: Six Pips (Greenwich Time Signal), WWV, WWVH, CHU, Jihō, Moscow Six Pips, and Australia's VNG. Sound them on the hour, every 15 minutes, or every minute. Bluetooth or AirPlay speaker running late? Measure its delay with the microphone and TrueOffset compensates. RADIO TIME CODES A clock sold as "atomic" is a radio listening to a distant station that spells out the time one second at a time. TrueOffset plays the codes of WWVB, DCF77, MSF, JJY (40 and 60 kHz), and BPC and shows each second being decoded as it is sent. Try setting a radio-controlled watch with it (beta), or switch on the DCF77 weather seconds to hear how Germany's station once sent a forecast. TRUEOFFSET MASTER CLOCK Our tribute to the U.S. Naval Observatory's telephone time service. A tick sounds every second while a voice announces your local time and then Universal Time, each ahead of a beep that lands on the true second. Prefer it quiet? Switch the voice off and keep the ticks. TrueOffset is not affiliated with the U.S. Naval Observatory. DUAL-STACK COMPARISON Ask one server over IPv4 and IPv6 side by side, to catch two different machines behind one name or a network that answers for both. FLEXIBLE TIME SOURCES Compare against Apple, Google, Cloudflare, NIST, US Naval Observatory, global NTP pools, or add your own servers. The default reference, ntp.trueoffset.app, is a Safran SecureSync 1200 with its own rubidium atomic clock. Set any source as your reference. QUALITY ANALYTICS Eight chart pages show the character of your time sources: - Overview — Every server at a glance - Offset History — Track drift over time - Offset Histogram — How the offsets are spread - Offset Range — Compare consistency across servers - Round Trip and Offset — See whether network delay moves the offset - Clock Sources — Decode reference clocks (GPS, PPS, Rubidium, Cesium) - IPv4 and IPv6 — Compare one server's two addresses - Rankings — Servers scored by jitter and round-trip time, with the steadiest named HELP IN THE APP What an offset is, why your clock drifts, what UTC and atomic time are, and what each screen shows, explained in the app. For anyone who cares how accurate their time really is, and wants to see the difference, not just trust it. Also on Apple TV. FOR TIMEKEEPERS: TRUEOFFSET FOR MAC Run your own time servers? The Mac app, free in this same listing, reads what they record about themselves and charts it, from six hours to a year: - NTPsec, ntpd, chrony, linuxptp, gpsd, Safran SecureSync, and Timebeat - Logs from a folder, or collected over SSH every hour, read-only - Offset, frequency, Allan deviation, temperature, peers, PTP, GNSS sky plots, and each machine's real-time clocks - Restarts, steps, and holdover found and marked, not averaged in - Your servers compared side by side as a fleet More at trueoffset.app/timekeepers --- In appreciation of Emerald Sequoia's Emerald Time.

"Prime Time" is a high-precision time app that shows the true time, accurate to the millisecond. It queries NTP servers directly — the same infrastructure that keeps the internet in sync — and works out the correct time from their answers. Your device's own clock is never used for the display. [New in version 1.4] • Display Offset (Pro): run the large clock up to 99.999 seconds ahead of or behind real time, in 1 ms steps — for remote broadcasts, live streams, or any delayed feed. While it is on, the time turns yellow, with the offset above and the actual time below, so there is no mistaking it for real time. Measurements are never shifted. • Server details now use two columns in landscape on iPhone, so everything fits on one screen. • On iPhone with ProMotion, the clock now refreshes up to 120 times a second. [Free — one server, in full detail] • Real-time sync with one NTP server of your choice • Every exchange laid open: address, stratum, reference, root delay, jitter, estimated error, and the last eight exchanges • Millisecond display, refreshed up to 120 times a second on ProMotion screens • Offset and round-trip time with sparkline history • Adaptive polling that eases off as a server proves steady [Pro — one-time purchase, no subscription] • Compare up to 30 servers. With three or more, a server that is off is outvoted instead of skewing the time shown. • Manual sync on demand • Keep the screen awake while the app is open • Display Offset: run the clock ahead of or behind real time A note on accuracy: a round trip is a single number covering two unknown halves, and nothing in the exchange reveals how it was divided. Prime Time widens the reported ± rather than inventing a correction to hide it. On cellular, where the two directions are least alike, that margin is wider — and shown. Made for developers, network engineers, broadcast crews, and anyone curious about how far off their device's clock really is. Available in English, Japanese, German, and French.