# std::chrono::ambiguous_local_time

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< cpp‎ | chrono

Defined in header `<chrono>` |  |
class ambiguous_local_time; |  | (since C++20)

Defines a type of object to be thrown as exception to report that an attempt was made to convert an ambiguous std::chrono::local_time to a std::chrono::sys_time without specifying a std::chrono::choose (such as `choose::earliest` or `choose::latest`).

This exception is thrown by std::chrono::time_zone::to_sys and functions that call it (such as the constructors of std::chrono::zoned_time that take a std::chrono::local_time).

Inheritance diagram

### Member functions

(constructor) | constructs the exception object (public member function)
operator= | replaces the exception object (public member function)
what | returns the explanatory string (public member function)

## std::chrono::ambiguous_local_time::ambiguous_local_time

template< class Duration > ambiguous_local_time( const std::chrono::local_time<Duration>& tp, const std::chrono::local_info& i ); | (1) | (since C++20)
ambiguous_local_time( const ambiguous_local_time& other ) noexcept; | (2) | (since C++20)

Constructs the exception object.

1) The explanatory string returned by what() is equivalent to that produced by os.str() after the following code:

    std::ostringstream os;
    os << tp << " is ambiguous.  It could be\n"
       << tp << ' ' << i.first.abbrev << " == "
       << tp - i.first.offset << " UTC or\n"
       << tp << ' ' << i.second.abbrev  << " == "
       << tp - i.second.offset  << " UTC";

The behavior is undefined if i.result != std::chrono::local_info::ambiguous.
2) Copy constructor. If *this and `other` both have dynamic type `std::chrono::ambiguous_local_time` then std::strcmp(what(), other.what()) == 0.

### Parameters

tp | - | the time point for which conversion was attempted
i | - | a std::chrono::local_info describing the result of the conversion attempt
other | - | another `ambiguous_local_time` to copy

### Exceptions

May throw std::bad_alloc

### Notes

Because copying a standard library class derived from std::exception is not permitted to throw exceptions, this message is typically stored internally as a separately-allocated reference-counted string.

## std::chrono::ambiguous_locale_time::operator=

ambiguous_locale_time& operator=( const ambiguous_locale_time& other ) noexcept; |  | (since C++20)

Assigns the contents with those of other. If *this and other both have dynamic type `std::chrono::ambiguous_locale_time` then std::strcmp(what(), other.what()) == 0 after assignment.

### Parameters

other | - | another exception object to assign with

### Return value

*this

## std::chrono::ambiguous_locale_time::what

virtual const char* what() const noexcept; |  | (since C++20)

Returns the explanatory string.

### Parameters

(none)

### Return value

Pointer to a null-terminated string with explanatory information. The string is suitable for conversion and display as a std::wstring. The pointer is guaranteed to be valid at least until the exception object from which it is obtained is destroyed, or until a non-const member function (e.g. copy assignment operator) on the exception object is called.

### Notes

Implementations are allowed but not required to override `what()`.

## Inherited from std::runtime_error

## Inherited from std::exception

### Member functions

(destructor) [virtual] | destroys the exception object (virtual public member function of `std::exception`)
what [virtual] | returns an explanatory string (virtual public member function of `std::exception`)

### See also

nonexistent_local_time (C++20) | exception thrown to report that a local time is nonexistent (class)

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