How to format a datetime to string using boost?

c++ formatting datetime

39,053

Solution 1

For whatever it is worth, here is the function that I wrote to do this:

#include "boost/date_time/posix_time/posix_time.hpp"
#include <iostream>
#include <sstream>

std::wstring FormatTime(boost::posix_time::ptime now)
{
  using namespace boost::posix_time;
  static std::locale loc(std::wcout.getloc(),
                         new wtime_facet(L"%Y%m%d_%H%M%S"));

  std::basic_stringstream<wchar_t> wss;
  wss.imbue(loc);
  wss << now;
  return wss.str();
}

int main() {
  using namespace boost::posix_time;
  ptime now = second_clock::universal_time();

  std::wstring ws(FormatTime(now));
  std::wcout << ws << std::endl;
  sleep(2);
  now = second_clock::universal_time();
  ws = FormatTime(now);
  std::wcout << ws << std::endl;

}

The output of this program was:

20111130_142732
20111130_142734

I found these links useful:

Solution 2

// create your date
boost::gregorian::date d(2009, 1, 7); 

// create your formatting
boost::gregorian::date_facet *df = new boost::gregorian::date_facet("%Y%m%d_%H%M%S"); 

// set your formatting
ostringstream is;
is.imbue(std::locale(is.getloc(), df));
is << d << endl;

// get string
cout << "output :" << is.str() << endl;

39,053

mackenir

Updated on August 26, 2020

Comments

mackenir over 3 years
I want to format a date/time to a string using boost.

Starting with the current date/time:
```
ptime now = second_clock::universal_time();
```
and ending up with a wstring containing the date/time in this format:
```
%Y%m%d_%H%M%S
```
Can you show me the code to achieve this? Thanks.
mackenir about 13 years

I'm testing this now - could be the wstringstream needs a wtime_facet and that's where it was silently failing for me.
CashCow about 13 years

That would work but note if you are going to use the same format for multiple dates, do not create the facet every time but create it once and then use it multiple times. The imbue itself is not expensive.
CashCow about 13 years

Note you would do that by storing the locale object.
matth over 12 years

Thanks, @CashCow. I made the changes you suggested.
Joshua Detwiler almost 7 years

For using C++98 and C++0x, I've found that using std::stringstream is better since the template is different for std::basic_stringstream.
romanz over 6 years

Guys, seriously. In C# I can write DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") and that's all! What the hell is wrong with C++ these days...
Validus Oculus about 6 years

You sounded like my nephew in high school :) I am sure that the function you mentioned does something very similar to what I coded above. If you want better user interface, then you have to build an abstraction layer over the boost. The boost is designed to be flexible. Take a look to Poco C++ Libraries. They have very nice Java style interface which makes it very easy to code. So problem is not about C++ :)
Steve Smith over 5 years

Is there a way to get it into a string variable (i.e. std::string) rather than output it directly to the console?
Aleksey F. over 2 years

@romanz, then try using your approach when the user defined format is used instead of yyyy-MM-dd HH:mm:ss, and a specific time zone, language/locale, encoding, first day of week and months/day shortenings are to be applied. And you get the hell of formats supported by DateTime, which do not cover all the cases.