Source: https://databento.com/docs/architecture/timestamping-guide


# Timestamping

![Databento timestamping diagram](https://databento.com/docs/timestamps.svg.md)

### Precision, accuracy, and resolution

In our documentation, we quantify these terms as follows:
- **Precision.** The maximum deviation between timestamps
delivered in the data and any reference time.
- **Accuracy.** The maximum deviation between timestamps delivered in the data
and Coordinated Universal Time (UTC).
- **Resolution.** An arbitrary unit of time. The minimum increment of
timestamps delivered in the data.
- **Jitter.** Closely related to precision. The maximum deviation of a clock's
periodicity from its intended periodicity.

> **Info**
>
> Unfortunately, common speech uses the opposite sign convention.
> A time source with **high precision** or **accuracy** is said to have low
> maximum deviation.  Likewise, **high resolution** refers to a small minimum
> timestamp increment. A clock with **high jitter** has low precision.

The following diagram helps to visualize these terms:

![Databento timestamping diagram](https://databento.com/docs/precision-vs-accuracy-vs-resolution.svg.md)

### Nanosecond resolution timestamps

You may have seen other data sources that claim to provide
nanosecond-*resolution* timestamps. But this is a meaningless
claim on its own, as any device is capable of nanosecond-resolution timestamps! You can
guess the current time and write a number arbitrarily down by hand to the
nanosecond resolution - that doesn't mean that your body is capable of
nanosecond-*precision* timestamping.

Likewise, you will find that most sources of financial data that carry
nanosecond-resolution timestamps will use software-based timestamping that
relies on CPU registers. There are a host of issues with this:
- The precision of CPU registers varies substantially with thermal conditions.
- The timestamping application is subject to sources of high jitter, such as
interrupts, kernel scheduler events, context switching, and interference from
other applications etc. This is especially the case with data providers that
use cloud-based virtual machines to capture the data.

To safeguard against these issues, we offload our timestamping to hardware,
for instance, FPGA, which achieves more deterministic results. Depending on the
techniques used, software timestamps may have a precision of anywhere from
100 nanoseconds to over 10 milliseconds. In contrast, our hardware timestamps
achieve a precision from 4 to 10 nanoseconds (depending on the
market).

### Time synchronization with Precision Time Protocol

You will also find that most sources of financial data rely on Network
Time Protocol (NTP) to synchronize their clocks. In practice, software
timestamps relying on NTP synchronization against public NTP servers can
deviate from UTC up to the order of 100 milliseconds. Typical implementations
of Precision Time Protocol (PTP) will achieve accuracy from sub-microsecond to somewhere under 50
microseconds.

At each data center, Databento uses a pair of GPS grandmaster clocks with PTP class 6 and
clock accuracy under 25 ns against UTC as the time source. Our data servers achieve
sub-microsecond synchronization to these GPS clocks.

### Accuracy, precision, and resolution of Databento timestamps

Databento's data is intended to be suitable for high fidelity simulation,
including backtesting of passive and arbitrage strategies, order routing,
transaction cost analysis, and execution research. Our receive
timestamps (`ts_recv`) have the following properties:
- **Precision.** We use hardware timestamping to achieve a precision from
4 to 10 nanoseconds.
- **Accuracy.** We use PTP time synchronization against GPS receiver-based
time sources that are backed up by rubidium atomic oscillators to ensure
holdover accuracy. Our timestamps achieve an accuracy from under 100
nanoseconds to under 1 microsecond, depending on the capture
server's location.
- **Resolution.** All of our timestamps are in nanosecond resolution.

Any exception to the above for a given dataset is stated in the
[detail page](https://databento.com/docs/schemas.md)
of the dataset. Such exceptions generally arise when we have to backfill
data for other sources or use different hardware for a particular market.

There is no guarantee that timestamps embedded by original publisher
or market (`ts_event`, `ts_in_delta`) will have high accuracy, precision, or
resolution. Some markets still use millisecond resolution timestamps,
inherited from legacy FIX protocol. Many markets will use NTP time
synchronization and software timestamps. Often, our timestamps will
have even higher precision and accuracy than those provided by the market
itself.