Exact time now, with seconds
This page compares your device clock with our server clock and shows the corrected time with seconds. Below it you see how far your clock is ahead or behind – with an honest error margin.
How it is calculated
How the offset is measured
Every web server response carries an HTTP Date header with the moment it was created – in UTC, to the second (RFC 9110, section 6.6.1). The page asks our server eight times and notes when each request left and when the answer arrived. Since the server stamped the answer somewhere in between, each sample gives a time window for the offset. The samples are spread over different fractions of a second, so the overlap of all windows becomes narrow – typically a few tenths of a second, less on a fast connection.
The large display is the corrected time: your device clock plus the measured offset. Your uncorrected device clock is shown below for comparison.
Example
A sample leaves at 12:00:04.900 (device clock), the answer arrives at 12:00:04.960, and the server stamp says “12:00:03”. So the server answered between 12:00:03.000 and 12:00:03.999 while the device showed 12:00:04.900 to 12:00:04.960. The device clock is therefore between 0.900 and 1.960 seconds fast. Seven more samples at other fractions of a second shrink this window.
Why device clocks drift
Computers and phones usually set their clock automatically over the internet (NTP) or the mobile network. If automatic time is switched off, the computer has been offline for a long time or the hardware clock battery is weak, the clock drifts – often by seconds per week.
Limits
- The reference is our server’s clock, not an atomic clock directly. RFC 9110 says servers with a clock ought to synchronize with UTC via NTP; if the server were off anyway, the result would be off too.
- Accuracy depends on your connection’s round-trip time. On unstable networks (mobile data, VPN) the window gets wider – the page always shows the error margin.
- The page cannot set your system clock. To fix it, turn on “Set time automatically” in your system settings.
Frequently asked questions
How accurate is the time shown?
As accurate as the measurement: the page shows the error margin, usually a few tenths of a second. It shrinks on a fast, stable connection and grows on mobile data or VPN.
Is this an atomic clock?
No. The reference is our server clock, which is meant to be synchronized with Coordinated Universal Time (UTC) via NTP. The page measures how far your device is off from it.
Why is my clock fast or slow?
Usually automatic time is turned off or the device was offline for a long time. Turn on “Set time automatically”, then measure again.
Does it show the time with seconds?
Yes, with seconds and tenths of a second. “Full screen” fills the whole display, for example in a classroom.
What data is sent?
Only eight short requests to our own server; the page reads the timestamp of the answer. Nothing is stored and no third-party service is contacted.
Sources and legal basis
- IETF RFC 9110 – HTTP Semantics, section 6.6.1 “Date” (response timestamp, UTC, NTP sync)
- MDN: Date HTTP header
As of:
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