# std::chrono::clock_cast

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< cpp‎ | chrono

Defined in header `<chrono>` |  |
template <class Dest, class Source, class Duration> auto clock_cast(const std::chrono::time_point<Source, Duration>& t); |  | (since C++20)

Converts the time point `t` of a clock `Source` to an equivalent time point of the clock `Dest`, using std::chrono::system_clock and/or std::chrono::utc_clock as intermediaries if necessary.

- If the expression std::chrono::clock_time_conversion<Dest, Source>{}(t) is well-formed, returns the result of that expression.
- Otherwise, if at least one of the following two expressions are well-formed, then

  - If both expression are well-formed, the conversion is ambiguous, and the program is ill-formed.
  - Otherwise, exactly one of the two expressions is well-formed; the result of that expression is returned.

1) std::chrono::clock_time_conversion<Dest, std::chrono::system_clock>{}(
std::chrono::clock_time_conversion<std::chrono::system_clock, Source>{}(t))
2) std::chrono::clock_time_conversion<Dest, std::chrono::utc_clock>{}(
std::chrono::clock_time_conversion<std::chrono::utc_clock, Source>{}(t))

- Otherwise, if at least one of the following two expressions are well-formed, then

  - If both expression are well-formed, the conversion is ambiguous, and the program is ill-formed.
  - Otherwise, exactly one of the two expressions is well-formed; the result of that expression is returned.

1) std::chrono::clock_time_conversion<Dest, std::chrono::utc_clock>{}(

std::chrono::clock_time_conversion<std::chrono::utc_clock, std::chrono::system_clock>{}(

std::chrono::clock_time_conversion<std::chrono::system_clock, Source>{}(t)))
2) std::chrono::clock_time_conversion<Dest, std::chrono::system_clock>{}(

std::chrono::clock_time_conversion<std::chrono::system_clock, std::chrono::utc_clock>{}(

std::chrono::clock_time_conversion<std::chrono::utc_clock, Source>{}(t)))

- Otherwise, this function does not participate in overload resolution.

### Return value

The result of the conversion, determined as described above.

### Example

| This section is incomplete Reason: no example

### See also

clock_time_conversion (C++20) | traits class defining how to convert time points of one clock to another (class template)

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