# set_calibration

## Description:

**set_calibration**(ClockTime @internal, ClockTime external, ClockTime rate_num, ClockTime rate_denom)

Adjusts the rate and time of this.

A rate of 1/1 is the normal speed of the clock. Values bigger than 1/1 make the clock go faster.

`internal`

and `external`

are calibration parameters that arrange that
get_time should have been `external`

at internal time ```
internal
```

. This internal time should not be in the future; that is, it should be less than the value of
get_internal_time when this function is called.

Subsequent calls to get_time will return clock times computed as follows:

``` C time = (internal_time - internal) * rate_num / rate_denom + external ```

This formula is implemented in adjust_unlocked. Of course, it tries to do the integer arithmetic as precisely as possible.

Note that get_time always returns increasing values so when you move the clock backwards, get_time will report the previous value until the clock catches up.

## Parameters:

this |
a Clock to calibrate |

external |
a reference external time |

rate_num |
the numerator of the rate of the clock relative to its internal time |

rate_denom |
the denominator of the rate of the clock |

internal |
a reference internal time |