Issue 1110: strftime %c and additional struct tm members

Authors: Jay Ghiron
Date: 2026-09-17
Submitted against: C2Y (N3886 draft)
Status: Open

The proposal N3272 added wording so that %z and %Z in strftime can use additional members in struct tm added by an implementation. However, %c and %Ec on some implementations also use these members to determine the time zone. For example: glibc with en_US.UTF-8 as seen on godbolt. The same wording should be copied to %c and %Ec to allow for additional members added by an implementation to be used.

Suggested correction

Modify N3886 7.31.3.6 (The strftime function) paragraph 3:

%c is replaced by the locale’s appropriate date and time representation. Behavior is implementation-defined if the broken-down time structure does not have a value that could be returned by localtime or gmtime. [all specified in 7.31.1members, including any non-standard additional members]