27 Time library [time]

27.11 Time zones [time.zone]

27.11.3 Exception classes [time.zone.exception]

27.11.3.2 Class ambiguous_­local_­time [time.zone.exception.ambig]

namespace std::chrono { class ambiguous_local_time : public runtime_error { public: template<class Duration> ambiguous_local_time(const local_time<Duration>& tp, const local_info& i); }; }
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ambiguous_­local_­time is thrown when an attempt is made to convert an ambiguous local_­time to a sys_­time without specifying choose​::​earliest or choose​::​latest.
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template<class Duration> ambiguous_local_time(const local_time<Duration>& tp, const local_info& i);
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Preconditions: i.result == local_­info​::​ambiguous is true.
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Effects: Initializes the base class with a sequence of char equivalent to that produced by os.str() initialized as shown below: 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";
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[Example 1: #include <chrono> #include <iostream> int main() { using namespace std::chrono; try { auto zt = zoned_time{"America/New_York", local_days{Sunday[1]/November/2016} + 1h + 30min}; } catch (const ambiguous_local_time& e) { std::cout << e.what() << '\n'; } }
Produces the output: 
2016-11-06 01:30:00 is ambiguous.  It could be
2016-11-06 01:30:00 EDT == 2016-11-06 05:30:00 UTC or
2016-11-06 01:30:00 EST == 2016-11-06 06:30:00 UTC
— end example]