# How Report Timestamps Work Source: https://docs.chain.link/data-streams/how-report-timestamps-work > For the complete documentation index, see [llms.txt](/llms.txt). Every Data Streams report carries two timestamps: - **`validFromTimestamp`** — when the report's price *starts being valid* - **`observationsTimestamp`** — when the report's price *was last observed*. Together, they describe a window of time rather than a single instant. This page explains how the two timestamps define a [report's window](#report-windows), what to expect when [no report exists for a given moment](#determining-current-price), and how timestamps apply to [Time Weighted Average Price (TWAP) streams](#twap-streams). ## Report windows A report does not have verified price for a single instant in time. The `validFromTimestamp` marks the beginning of the window, and the `observationsTimestamp` marks the end. Both fields are Unix timestamps in seconds. [Each report schema](/data-streams/reference/report-schema-overview) contains definitions, including the unit of time, for all fields. The window of time can vary depending on how frequently the Decentralized Oracle Network (DON) can observe the data and generate reports. Windows are contiguous by construction: each one starts immediately following the previous window. Each report is designed to have no gaps or overlap, with every time interval belonging to exactly one report. ## Determining current price Because each report covers a window rather than an instant, the "current" price at any given moment is the price of the report whose window contains that moment. Whether such a report exists yet depends on how recently the DON observed the data and delivered the report. **Normal case: a report exists at that exact moment** For example, a report exists with `observationsTimestamp = 12:05:00` and a 1-second window. The report is delivered slightly after `12:05:00` (for reports with second-precision timestamps, typically up to 1-2 seconds later) due to DON consensus and transmission. **Edge case: no report at that exact moment** It is possible for no report to be observed with `observationsTimestamp = 12:05:00`. For example: - Last report: `observationsTimestamp = 12:04:59` - Next report: `observationsTimestamp = 12:05:01` The next report's `validFromTimestamp` is `12:05:00`, absorbing the gap and creating a 2-second window (`12:05:00` → `12:05:01`). In this example, the price for `12:05:00` is observed one second later at `12:05:01`. Because windows can vary in width, **do not assume every report covers the same window**. Read `validFromTimestamp` and `observationsTimestamp` from each report rather than deriving the window from the previous report's timestamp or from your own clock. ## TWAP streams Time Weighted Average Price (TWAP) streams report the average price over a rolling window, rather than a single observed price. A TWAP report is an **aggregated calculation** derived from the underlying reports. See the [TWAP report schema](/data-streams/reference/report-schema-v2#time-weighted-average-price-twap) for the full field definitions. A TWAP window is anchored to the latest observation and moves forward with each new report. Unlike standard streams, it doesn't align to the clock or snap to round numbers. For example, a 60-second TWAP requested "at `12:05:01`" covers `12:04:01` → `12:05:01`. **Formula:** ``` TWAP = (sum of price × duration for each report in the window) / window length in seconds ``` - 30-second TWAP → divide by 30 - 60-second TWAP → divide by 60 The TWAP is constructed from the underlying reports that fall within its window. Each underlying report normally covers about 1 second, but if a report's window is wider because it absorbed a gap, its price is weighted across the full window it covers.