what is the intuition behind this?

```
# 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))
```