Comparison

AtomicClock vs GMT Time

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

Head to head
About

AtomicClock

This app displays the exact current time synchronized with NTP servers, offering a customizable clock view for precise time checks. It's ideal for setting watches, verifying timestamps, or comparing local and network time.

Highlights
  • Precise time from NTP servers
  • Customizable clock faces
  • Select or add time servers
  • Local and UTC views
  • 12/24 hour modes
  • Customizable time format
  • Acoustic ticking
Features
Read full description

Check precise NTP reference time at a glance. AtomicClock helps you set watches, wall clocks, cameras, and other devices, compare local time with UTC, and follow moments when every second matters. Clear analog and digital time AtomicClock displays current time from NTP servers that reference atomic clocks. Choose a predefined server or add your own, then view local or UTC time in a clean analog or digital clock. Customize your reference clock • Switch between 12-hour and 24-hour time • Customize the time format • Choose from multiple clock faces and hands • Use a smooth, fluid second hand • Add acoustic ticking or the Greenwich Time Signal • Tap the screen to hide information and controls, freeze the display, or mute ticking Details for precise time checks View technical NTP information, including round-trip time and server stratum. Whether you are checking a timestamp, preparing a camera, aligning a wall clock, or setting a watch by hand, the seconds remain clear and easy to follow. AtomicClock is free to use. AtomicClock Pro is available as a one-time purchase with no subscription. It unlocks your preferred clock face, hands, and font, removes ads, and includes upcoming Pro features. AtomicClock displays NTP reference time for comparison and does not change your device’s system time. Results can vary with the selected server, network conditions, and device behavior.

About

GMT Time

This app provides accurate GMT time using NTP protocol and TrueTime framework. It offers a timekeeping function, allows setting time between two locations for itineraries, and supports multiple languages. Enjoy precise timekeeping with 1/100 second accuracy.

Highlights
  • Accurate GMT time display
  • NTP and TrueTime framework integration
  • Timekeeping function (on/off)
  • Set time between two locations
  • Multi-language support (English, Japanese, Chinese, Cantonese)
  • 1/100 second accuracy
Features
Read full description

NEW IN 1.2: SIMPLE MODE AND MINUTE REPEATER Tap the accessibility icon at the top right of Settings to switch to Simple mode. Local time, manual announcements and settings are on one page. Schedule time windows by weekday with half-hourly or hourly announcements. MINUTE REPEATER GUIDE 1. Choose vibration separately for normal and Silent modes, and whether voice should play in Silent mode. 2. Set Vibration frequency and try the preview. Hourly is the default. Start the announcer to run vibration on its own schedule. 3. Count hours, quarters and remaining minutes, in that order, using a 12-hour clock. At 3:37: 3 long pulses, 2 long-short pairs, 7 short pulses. Each quarter represents 15 minutes. Bell previews use low tones for hours, high-low pairs for quarters and high tones for remaining minutes. Vibration requires a supported iPhone; the feel varies by device and foreground/background state. Background patterns use strong-weak pairs. Background use requires Pro Lock Screen announcements and depends on system and app state. Stopping announcements or entering quiet hours stops scheduled vibration; in-app mute stops sound only. Foreground manual announcements and bell previews can play in Silent mode. Time117 brings network time synchronization, spoken announcements, world clocks and watch records together for everyday timekeeping, travel and collecting. • Spoken time: start or stop announcements, adjust speech speed and signal sounds, and set quiet hours. • World time: choose home and destination zones, share times and set alarms. • Clock views: themes, a large desk clock, widgets and Siri shortcuts. • Watch accuracy: track one watch for free, record offsets and view daily-rate trends. • Acoustic estimates: record mechanical watch ticks with the microphone. When the signal is sufficient, see beat-rate and daily-rate estimates during recording, then confirm and save the full measurement. • Watch standards: explore reference information and official source links. Time117 Pro is a one-time lifetime purchase. It unlocks background and Lock Screen announcements, hourly and custom intervals, ad removal, multiple-watch tracking, and editing collection photos, purchase details and service records. Purchases can be restored. Background announcements support Live Activities and the Dynamic Island on compatible iPhone models. Available in English, Japanese, Traditional and Simplified Chinese, Korean, Spanish, French, German, Brazilian Portuguese, Russian and Indonesian. Collection records and photos stay on your device; there is no built-in cloud sync. Service dates do not schedule reminders. Network time accuracy depends on network and device conditions. Acoustic results are estimates affected by the environment, placement and phone audio clock; they do not replace a professional timegrapher or certification.

Screenshots

AtomicClock4 screens
GMT Time4 screens

Verdict

The call

The clearest difference is update cadence: AtomicClock at monthly against GMT Time's every 28 months. AtomicClock also leads on ratings volume (5.6K vs 38). GMT Time's advantage is monetization model (ad-supported vs free with in-app purchases). On price, rating, ads and in-app purchases 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. AtomicClock sells 1 one-off in-app purchase and GMT Time sells 1 one-off in-app purchase. Whichever you choose, the download price is not the number that matters.

ReceptionRating · Positive reviews · Number of ratings

On the App Store both sit at effectively the same score — 4.8 for AtomicClock against 4.7 for GMT Time. That said, the two scores are not equally well evidenced: AtomicClock has 5.6K ratings behind it against 38, so its average is the more settled of the two.

UpkeepUpdate frequency

AtomicClock ships an update monthly, GMT Time every 28 months. The most recent releases landed on October 29, 2026 and October 30, 2026 respectively.

Scorecard3 real differences · 7 level
AtomicClock versus GMT Time: the parameters behind the verdict, then further details
ParameterAtomicClockGMT Time
PriceFreeFree
Rating4.8 (5.6K ratings) — better4.7 (38 ratings)
Positive reviews84.3% of reviews—
Number of ratings5.6K — better38
Update frequencyMonthly — betterEvery 28 months
AdsYesYes
In-app purchasesYesYes
MonetizationFree with in-app purchasesAd-supported — better
DevicesiPhone, iPadiPhone, iPad
Requires iOS17.417.0 — better
Further details — not scored
Size17 MB26 MB
Age rating4+4+
DeveloperTimo PartlMingChun Chien

Customer experience

AtomicClock

All ratings5,568 ratings
Positive96.5%
Neutral1.7%
Negative1.8%
Written reviews242 reviews
Positive84.3%
Neutral3.3%
Negative12.4%

GMT Time

All ratings38 ratings
Positive89.5%
Neutral7.9%
Negative2.6%

Bugs and requests

AtomicClock

Reported bugs

3 issues
  • Crashes on certain iOS versions
  • Occasional freezing of hands
  • Countdown timer sound not working

Requested features

5 requests
  • Add GMT/dual time display
  • Implement widget support
  • Add different second hand sounds
  • Allow setting background color to match watch
  • Include alarm/timer functionality

GMT Time

Not enough reviews yet to summarise bugs or requests.

In-app purchases

1 purchases

AtomicClock

One-time1
  • Lifetime Pro Version$6.99
1 purchases

GMT Time

One-time1
  • Time117 Pro$0.99

Questions

Is AtomicClock free?
AtomicClock is free to download, with in-app purchases available.
Is GMT Time free?
GMT Time is free to download, with in-app purchases available.
Which has better reviews, AtomicClock or GMT Time?
AtomicClock is rated higher. AtomicClock averages 4.8 out of 5 from 5.6K ratings, while GMT Time averages 4.7 from 38 ratings.
Do AtomicClock or GMT Time have ads?
Both AtomicClock and GMT Time show ads.
Which is updated more often, AtomicClock or GMT Time?
AtomicClock ships an update monthly, and GMT Time every 28 months. Most recently, AtomicClock was updated on October 29, 2026 and GMT Time on October 30, 2026.

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