Chronometer for the Web
A web port of Emerald Chronometer (GitHub), an astronomical watch-face app originally built for iPhone and iPad.
View the project on GitHub · Credits · Privacy · Support · Disclaimer
Your settings are saved in this browser's local storage on this device. Use the Share button to copy a link to a view. See Privacy for more information.
Other Apps
A web port of Emerald Chronometer (GitHub), an astronomical watch-face app originally built for iPhone and iPad.
A web port of Emerald Observatory (GitHub), an astronomical clock app originally built for iPad.
A live data explorer for the astronomy engine shared by Chronometer and Observatory — rise/set times, planetary positions, and calendar and clock values, at any time and location.
Thirty years of solar and lunar eclipses, each with links that open the moment and place of maximum eclipse in Observatory and Chronometer.
General Help Topics
Privacy
Emerald Chronometer for the Web
Overview
Emerald Chronometer for the Web is a fully client-side application. It runs entirely in your browser and does not communicate with any application server for its core functionality.
Data Collection
The app itself does not collect, store, or transmit any personal data to any application server. There are no app-level analytics, tracking pixels, cookies, or telemetry of any kind.
Web Server Logs
When the app is served over HTTP or HTTPS, the hosting provider (SiteGround) records standard web server access logs for each page and resource request. These logs include:
- Your IP address
- The URL requested. The app normally keeps the URL clean; query-string parameters (latitude, longitude, city name, timezone, etc.) appear only when you create or open a shared link
- Timestamp, HTTP status code, referrer, and browser user-agent string
These logs are retained by SiteGround for up to 30 days and are used solely for security monitoring and troubleshooting. They are not analyzed for user tracking purposes.
When running from file:// URLs (a local copy of the app), no
server is involved and no logs are generated.
Map Tile Requests
When you use the location dialog (on pages served via http:// or
https://), the app fetches map tile images from
OpenStreetMap
to display a preview of the selected location.
These requests are standard image fetches and do not include any metadata identifying the tile coordinates as your location — OpenStreetMap sees only which map tile was requested, the same as any map browsing.
Browser Location (Geolocation API)
If you tap "Use device location via browser", the app uses the browser's Geolocation API to obtain your coordinates. This data is processed entirely within the browser — the app never sends it to any application server.
The resolved coordinates are matched against a bundled database of approximately 47,000 cities to display a human-readable location name. This reverse-geolocation lookup happens entirely in the browser — no external geocoding service is contacted.
Local Storage & Sharing
The app saves your settings (location, time, and per-app configuration) in your browser's local storage — on your device only. This data is never sent to any application server, and it persists across visits without any cookies.
You can clear local storage at any time through your browser's settings (typically alongside your browsing history).
When you use the Share button, the app builds a URL that encodes the current view so you can send it to someone else or open it on another device. Opening such a link lets you either use those settings just for that visit or save them as your defaults.
Note: Because shared links carry settings as URL query
parameters, those parameters are visible in your browser history and, when
served over HTTP or HTTPS, in the hosting provider's access logs — but only for
links you deliberately create or open. On file:// pages where
local storage is unavailable, the app falls back to keeping settings in the
URL.
Third-Party Services
- OpenStreetMap (map tiles only, HTTP/HTTPS only) — governed by OSM's privacy policy.
Contact
For questions about this privacy policy, please visit the project on GitHub.
Last updated: May 2026
Support
Emerald Chronometer for the Web
Found a bug? Please report it on the GitHub issues page. Describe what you saw and what you expected, and mention which app and which browser and device you were using, along with the app’s version number (shown at the bottom of the help popup opened by the ℹ︎ button, e.g. “v2.1.8”).
This free web app is maintained by volunteers, so no support or response time is promised — but the developers do read the reports and fix most bugs.
The website itself only serves, as a convenience, files available from the GitHub releases page (see instructions for running the app here).
Disclaimer
Emerald Chronometer for the Web
THIS FREE WEB APP IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
The pages served to your browser are available at the GitHub releases page (see instructions for running the app here).
Geneva takes its name from the city in Switzerland
, home to many of the world's finest watchmakers.
Geneva is a complex multi-dial face with many traditional complications plus a
few modern twists. There are 21 hands plus 9 additional indicators. The hours,
minutes and seconds are standard (but with no numbers on the dial). There is
an am/pm dot just above the 12 o'clock position (white for am, black for pm).
The thin gray-blue hand with the circle on the outermost dial indicates the
day of the month.
The first twist on the classic look is that the day numbers 29 thru 31 appear
only as needed. To the left, for example, is the appearance for Nov 29, 294
CE.
The white hand with a black tip indicates the last two digits of the year,
read against
the inner gray dial with 100 divisions (zero is at the 12 o'clock position).
The thin white hand with a red tip indicates the two digit century, read
against the same dial. The example to the right shows the year 408 CE.
The primary hand of the subdial at 12 o'clock indicates the month. The interior region of that dial, which is marked with the seasons, rotates so that the boundaries between the seasons are properly aligned to the calendar months (though this rotation is tiny since the Gregorian reform; it was a whole month in 6000 BCE).
For more precision, the tiny hand in the seasons subdial changes at the exact
time of each equinox and solstice (not just the beginnings of the usual days).
Both are correct for both hemispheres (the example at left shows a southern
hemisphere case).
The primary hand on the subdial at 3 o'clock simply shows the current local
time in 24-hour format
while the small gray-green arrow shows the
UT
hour. The local time always follows the local daylight savings time rules (for
most jurisdictions; UT never uses DST). If daylight savings time is in effect
a "D" will appear in the lower left quadrant; otherwise, an "S" will appear in
the lower right. A "+" will appear in the upper right quadrant if the UT date
is a day ahead of the local date, and a "-" will appear in the upper left if
it is a day behind; otherwise both upper quadrants will be blank.
The primary hand on the subdial at 9 o'clock shows the day of the week.
The tiny hand is another of Geneva's twists, a fully general leap year
indicator. It points to 1, 2 or 3 in common years and 4 in regular leap years.
But the
Gregorian calendar
skips 3 leap years every 400 years so the tiny hand points at 100 or 400 if
one of the centurial rules applies. This is known as a "secular perpetual
calendar" in horology jargon.
The four small subdials indicate the times of the sunrise, sunset, moonrise
and moonset events for the current day.
The moonrise and moonset dials have am/pm dots above. If there is no event for
the current day the corresponding dial will read 12:00 and the am/pm dot will
be red.
The final twist is the moon phase indicator which shows a realistic terminator, rotated to match its actual orientation in the sky, exactly like the one on Chandra. Superimposed on this is a retrograde hand showing the age of the current lunation.