Proposed resolution:

This wording is relative to N4849.

1. Modify [time.zone.zonedtime.overview], class template zoned_time synopsis, as indicated:

   template<class Duration2, class TimeZonePtr2>
   zoned_time(string_view name, const zoned_time<Duration2, TimeZonePtr2>& zt);
   template<class Duration2, class TimeZonePtr2>
   zoned_time(string_view name, const zoned_time<Duration2, TimeZonePtr2>& zt, choose);

2. Modify [time.zone.zonedtime.ctor] as indicated:

   template<class Duration2, class TimeZonePtr2>
   zoned_time(string_view name, const zoned_time<Duration2, TimeZonePtr2>& y);
   

   -32- Constraints: zoned_time is constructible from the return type of traits::locate_zone(name) and zoned_time<Duration2, TimeZonePtr2>.

   -33- Effects: Equivalent to construction with {traits::locate_zone(name), y}.

   template<class Duration2, class TimeZonePtr2>
   zoned_time(string_view name, const zoned_time<Duration2, TimeZonePtr2>& y, choose c););
   

   -34- Constraints: zoned_time is constructible from the return type of traits::locate_zone(name), zoned_time<Duration2, TimeZonePtr2>, and choose.

   -35- Effects: Equivalent to construction with {traits::locate_zone(name), y, c}.

   -36- [Note: The choose parameter has no effect. — end note]

[ 2020-02 Status to Immediate on Thursday morning in Prague. ]

[ 2020-02-13, Prague ]

During LWG discussions it was suggested to rebase the wording to reduce the chances for confusion.

zoned_time constructors with string_view and another zoned_time are not accepting zoned_time instances that use a different time zone representation (TimeZonePtr parameter):

zoned_time(string_view name, const zoned_time<Duration>& zt);
zoned_time(string_view name, const zoned_time<Duration>& zt, choose);

This makes them inconsistent with the constructors from TimeZonePtr and zoned_time, that they delegate to:

template<class Duration2, class TimeZonePtr2>
  zoned_time(TimeZonePtr z, const zoned_time<Duration2, TimeZonePtr2>& zt);
template<class Duration2, class TimeZonePtr2>
  zoned_time(TimeZonePtr z, const zoned_time<Duration2, TimeZonePtr2>& zt, choose);

Furthermore it forces the creation of a temporary zoned_time object in case when the source uses the same TimeZonePtr, but different Duration.

This wording is relative to N4820.

1. Modify [time.zone.zonedtime.overview], class template zoned_time synopsis, as indicated:

   template<class Duration2, class TimeZonePtr2>
   zoned_time(string_view name, const zoned_time<Duration2, TimeZonePtr2>& zt);
   template<class Duration2, class TimeZonePtr2>
   zoned_time(string_view name, const zoned_time<Duration2, TimeZonePtr2>& zt, choose);

2. Modify [time.zone.zonedtime.ctor] as indicated:

   template<class Duration2, class TimeZonePtr2>
   zoned_time(string_view name, const zoned_time<Duration2, TimeZonePtr2>& y);
   

   -32- Remarks: This constructor does not participate in overload resolution unless zoned_time is constructible from the return type of traits::locate_zone(name) and zoned_time<Duration2, TimeZonePtr2>.

   -33- Effects: Equivalent to construction with {traits::locate_zone(name), y}.

   template<class Duration2, class TimeZonePtr2>
   zoned_time(string_view name, const zoned_time<Duration2, TimeZonePtr2>& y, choose c););
   

   -34- Remarks: This constructor does not participate in overload resolution unless zoned_time is constructible from the return type of traits::locate_zone(name), zoned_time<Duration2, TimeZonePtr2>, and choose.

   -35- Effects: Equivalent to construction with {traits::locate_zone(name), y, c}.

   -36- [Note: The choose parameter has no effect. — end note]