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Showing content from http://en.cppreference.com/w/cpp/algorithm/../../cpp/header/../locale/time_get/get.html below:

std::time_get<CharT,InputIt>::get, std::time_get<CharT,InputIt>::do_get - cppreference.com

Parses the date and time from the input character sequence

according to the format provided in the character sequence

. The format is expected to follow the format described below, although actual processing of each format specifier can be customized by overriding

. The

function performs the following: First, clears the error bits in

by executing

. Then enters a loop, which terminates whenever any of the following conditions becomes true (checked in this order):

a) All characters have been read from the format string (fmtbeg == fmtend).

c) All characters have been read from the input sequence (beg == end. If this condition terminates the loop, the function sets both eofbit and failbit in err.

In the body of the loop, the following steps take place:

If the next character in the format string is

, followed by one or two characters that form a valid

conversion specifier (see below), these characters are used in the call

, where

is the primary conversion specifier character, and

is the optional modifier (which appears between

and the format character, if present). If there is no modifier, the value

is used. If the format string is ambiguous or ends too early to determine the conversion specifier after

,

is set in

and the loop is terminated. If, after the call to

, no error bits are set in

, the function increments

to point right after the conversion specifier and continues the loop.

If the next character is whitespace, as indicated by the locale provided in the stream

(i.e.

, the function keeps incrementing

until it either becomes equal to

or points to a non-whitespace character.

c) If the next character in the format string is equivalent to the next character in the input stream according to case-insensitive comparison, the function advances both sequences by one character ++fmtbeg, ++beg; and continues the loop, Otherwise, it sets the failbit in err.

Parses one conversion specifier from the input sequence

and updates the

structure pointed to by

accordingly.

First, clears the error bits in err by executing err = std::ios_base::goodbit. Then reads characters from the input sequence [beg, end) that are expected by the std::time_get format specifier formed by combining '%', modifier (if not '\0'), and format. If the characters do not combine to form a valid conversion specifier, sets failbit in err. If the end of the input stream is reached after reading a character, sets eofbit in err. If the input string was parsed successfully, updates the corresponding fields of *t.

For complex conversion specifiers, such as '%x' or '%c', or the directives that use the modifiers 'E' and 'O', the function may fail to determine some of the values to store in *t. In such case, it sets eofbit in err and leaves these fields in unspecified state.

The format string consists of zero or more conversion specifiers, whitespace characters, and ordinary characters (except %). Each ordinary character is expected to match one character in the input stream in case-insensitive comparison. Each whitespace character matches arbitrary whitespace in the input string. Each conversion specification begins with % character, optionally followed by E or O modifier (ignored if unsupported by the locale), followed by the character that determines the behavior of the specifier. The format specifiers match the POSIX function strptime():

Note: tm_isdst is not written to, and needs to be set explicitly for use with functions such as mktime

Iterator pointing one past the last character in [beg, end) that was parsed successfully.

The case-insensitive comparison for the non-whitespace non-'%' characters in the format string, the std::collate facet of the locale provided by str is typically, but not necessarily, used.

If a parsing error is encountered, many implementations of this function leave *t completely untouched.

It's unspecified if these functions zero out the fields in *t that they do not set directly: portable programs should initialize every field to zero before calling get().

#include <iomanip>
#include <iostream>
#include <locale>
#include <sstream>
 
int main()
{
    std::istringstream ss("2026-März-12 23:45:56");
    ss.imbue(std::locale("de_DE.utf8"));
 
    auto& f = std::use_facet<std::time_get<char>>(ss.getloc());
    std::tm t{};
    std::string s = "%Y-%b-%d %H:%M:%S";
    std::ios_base::iostate err = std::ios_base::goodbit;
    auto ret = f.get({ss}, {}, ss, err, &t, &s[0], &s[0] + s.size());
    ss.setstate(err);
    std::istreambuf_iterator<char> last{};
 
    if (ss)
    {
        std::cout << "Successfully parsed as " << std::put_time(&t, "%c") << '\n';
        if (ret != last)
        {
            std::cout << "Remaining content: ";
            std::copy(ret, last, std::ostreambuf_iterator<char>(std::cout));
        }
        else
            std::cout << "The input was fully consumed.";
    }
    else
    {
        std::cout << "Parse failed.\nUnparsed string: ";
        std::copy(ret, last, std::ostreambuf_iterator<char>(std::cout));
    }
    std::cout << '\n';
}

Output:

Successfully parsed as Sun Mar 12 23:45:56 2026
The input was fully consumed.

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