With Boost datetime how do i create a month string padded with zero?

Question

With Boost datetime how do i create a month string padded with zero for the first 9 months?

So I need "05" not "5".

date Date(2012,05,1);

string monthStringAsNumber = lexical_cast<string>(date.Month().as_number()); 
// returns "5"

string monthStringAsNumberTwo = date.Month().as_short_string();
// returns "Aug"

I would like "05". How do i do this?

Thanks a lot.

Do you need to use `lexical_cast`? http://stackoverflow.com/questions/1714515/how-can-i-pad-an-int-with-leading-zeros-when-using-cout-operator — HostileFork says dont trust SE, May 17 '12 at 14:50
i use lxeical_cast to cast from the int returned by as_number to string. — CodingHero, May 17 '12 at 14:55
Yes...but if you were using a stringstream (or something of that sort) you could use ``'s `setfill` and `setw`, as in the link above... — HostileFork says dont trust SE, May 17 '12 at 14:58

score 4 · Accepted Answer · answered May 17 '12 at 15:25

You don't really need lexical_cast The following should work:

stringstream ss;
ss << setw(2) << setfill('0') << date.Month().as_number());
string monthStringAsNumber = ss.str();

or you could just go for this howler:

const string mn[] ={ "01", "02", "03", "04", "05", "06",
                     "07", "08", "09", "10", "11", "12" };
const string& monthStringAsNumber = mn[ date.Month().as_number() ];

score 1 · Answer 2 · answered May 17 '12 at 15:45

In general, if you want to get the date time in some customized format, you could check http://www.boost.org/doc/libs/1_49_0/doc/html/date_time/date_time_io.html, e.g.

#include <boost/date_time.hpp>
#include <iostream>
#include <sstream>
#include <string>

int main(int argc, char** argv)
{
    boost::gregorian::date date (2012,5,1);
    boost::gregorian::date_facet* facet = 
            new boost::gregorian::date_facet("%Y %m %d");
    // ^ yes raw pointer here, and don't delete it.
    std::ostringstream ss;
    ss.imbue(std::locale(std::locale(), facet));
    ss << date;
    std::string s = ss.str();

    std::cout << s << std::endl;   // 2012 05 01
    return 0;
}

With Boost datetime how do i create a month string padded with zero?

2 Answers2