Hello,

I couldn’t find any.

Could anyone point me towards a tutorial or anything that might help me get acquainted with the timestamp conversion concept introduced in the **Feature Engineering with Weather Data** lab ?

It says :

`a simple approach to generate a periodic signal is to use sine and cosine to convert the timestamp to clear "Time of day" ( `

Day sin`,`

Day cos`) and "Time of year" (`

Year sin`,`

Year cos` ) signals.`

```
# Convert timestamps into periodic signals
outputs['Day sin'] = tf.math.sin(timestamp_s * (2 * pi / day))
outputs['Day cos'] = tf.math.cos(timestamp_s * (2 * pi / day))
outputs['Year sin'] = tf.math.sin(timestamp_s * (2 * pi / year))
outputs['Year cos'] = tf.math.cos(timestamp_s * (2 * pi / year))
```

I’m lost here.