12 / Tools & discovery
Math7 Time — Precise time and RTC calibration
Math7 Time shows how far your device clock is from the server's chrony-disciplined clock and gives RTC values for setting hardware clocks, with a drift calculator in seconds per day and ppm.
- Access
- Public — no account needed
- Runs on
- Caddy time API · chrony
- Live status
- Checking
Who it is for
- Makers setting DS1307, DS3231, or PCF8563 real-time clocks
- Anyone checking whether a computer or phone clock is off
- Engineers estimating crystal drift
What you can do
Measured offset
Eight NTP-style round trips pick the fastest exchange; the accuracy shown is half that round trip.
RTC formats
Unix seconds, milliseconds, and hex; ISO 8601; ISO week; day of year; and BCD register values.
Second marker
A visual tick and an optional audio tick help you set a clock by hand.
Drift calculator
Convert an observed error into seconds per day and parts per million.
Getting started
- 01
Open time.math7.com and wait a moment for the offset measurement.
- 02
Read corrected UTC or local time, or copy the RTC values you need.
- 03
Use the drift calculator after comparing a clock over several days.
Access
Math7 Time is public and needs no account.
Privacy and data
The page only asks the server for its current time. It publishes the server's sync status but never the upstream time server address.
Common questions
How accurate is it?
The page reports its own accuracy, which is half the fastest measured round trip to the server.
Why are BCD values listed?
Many RTC chips store time in BCD registers; the page lists them in the chip's register order.