# Measuring elapsed time (deprecated)

:::{important}
Legacy Telemetry collection APIs are now deprecated.
Please use Glean instead.
:::

To make it easier to measure how long operations take, we have helpers for C++.
These helpers record the elapsed time into histograms, so you have to create suitable {doc}`histograms` for them first.

API:

```cpp
void AccumulateTimeDelta(HistogramID id, TimeStamp start, TimeStamp end = TimeStamp::Now());
void AccumulateTimeDelta(HistogramID id, const nsCString& key, TimeStamp start, TimeStamp end = TimeStamp::Now());
```
