Comparison

TrueOffset vs CalMirror

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

TrueOffset

This app precisely measures your device's clock accuracy against global time servers. It offers multiple clock faces, time scales, and audible time signals, including radio time codes. Analyze time source quality with detailed charts and compare IPv4/IPv6 responses.

Highlights
  • NTP server comparison
  • Multiple clock faces (analog, digital, NTP offset)
  • UTC & TAI time scales
  • Audible time signals and radio time codes
  • Dual-stack IPv4/IPv6 comparison
  • Flexible time source selection
  • Quality analytics charts
Features
Read full description

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.

About

CalMirror

Read full description

Have you got 2 or 3 Google accounts? Work, personal, side projects — calendars all over the place, double bookings, endless copy-paste? CalMirror automatically mirrors events between your multiple Google Calendars. ------------------ PERFECT FOR • People with separate work and personal Google accounts • Side hustlers who don't want freelance work showing on their main calendar • Freelancers who want to share busy times — not details — with family • Anyone working across multiple Google Workspaces KEY FEATURES • Auto sync events from Calendar A to Calendar X • Replace titles and notes (e.g., "Client X meeting" → "Busy") • Color conversion rules • Filter out events you don't want to sync (Pro) • Auto-delete sync (Pro) • Run multiple sync rules in parallel (Pro) FREE / PRO • Free: 1 sync rule • Pro ($3.99/month): Unlimited rules + filters + deletion sync PRIVACY • Calendar data is never stored on our servers • Official Google OAuth 2.0 authentication REQUIREMENTS iOS 16+ / Google account ------------------ Terms of Use: https://cal-mirror.bad-company.jp/terms Privacy Policy: https://cal-mirror.bad-company.jp/privacy Apple Standard EULA: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/

Screenshots

TrueOffset4 screens
CalMirror4 screens

Verdict

The call

The clearest difference is in-app purchases: TrueOffset at none against CalMirror's 2. TrueOffset also leads on ads (none vs shown). CalMirror's advantage is iOS requirement (15.1 vs 17.6). On price, update cadence and device support there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Both are free to download. CalMirror sells 2 in-app purchases, starting at $2.99 per month. TrueOffset asks for nothing beyond the download.

UpkeepUpdate frequency

TrueOffset ships an update fortnightly, CalMirror every 3 weeks. Both last shipped on October 28, 2026.

Scorecard3 real differences · 7 level
TrueOffset versus CalMirror: the parameters behind the verdict, then further details
ParameterTrueOffsetCalMirror
PriceFreeFree
Rating4.9 (8 ratings) — better—
Positive reviews100.0% of reviews—
Number of ratings8 — better—
Update frequencyFortnightly — betterEvery 3 weeks
AdsNo — betterYes
In-app purchasesNo — betterYes
MonetizationFree—
DevicesiPhone, iPad, Apple TViPhone, iPad, iPod
Requires iOS17.615.1 — better
Further details — not scored
Size4 MB40 MB
Age rating4+4+
DeveloperRichard Bollarbad-company Incorporated

In-app purchases

None

TrueOffset

No in-app purchases

2 purchases

CalMirror

Subscriptions2
  • Premium Monthly$2.991 Month
  • Premium Yearly$29.991 Year

Questions

Is TrueOffset free?
TrueOffset is free to download, with no in-app purchases.
Is CalMirror free?
CalMirror is free to download, with in-app purchases available.
Do TrueOffset or CalMirror have ads?
CalMirror shows ads; TrueOffset does not.
Which is updated more often, TrueOffset or CalMirror?
TrueOffset ships an update fortnightly, and CalMirror every 3 weeks. Most recently, TrueOffset was updated on October 28, 2026 and CalMirror on October 28, 2026.

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