Using Boost.DateTime to parse a tweet’s timestamp

Here is a sample tweet timestamp as requested through their API.

Thu Jun 09 00:06:02 +0000 2011

In order to parse this tweet using the Boost Date Time library, we can use the following code.

#define BOOST_ALL_DYN_LINK
#include <iostream>
#include <boost/date_time/posix_time/posix_time.hpp>
#include <boost/date_time/posix_time/posix_time_duration.hpp>
#include <boost/date_time/c_local_time_adjustor.hpp>

int main()
{
    using namespace boost::posix_time;
    std::string format = "%a %b %d %H:%M:%S +0000 %Y";
    std::string tweetTimeString = "Thu Jun 08 00:06:02 +0000 2011";
    ptime tweetTime;

    time_input_facet facet(format, 1);

    std::stringstream ss(tweetTimeString); 
    ss.imbue(std::locale(ss.getloc(), &facet));
    ss >> tweetTime;

    std::cout << "Time: " << tweetTime << std::endl; 
    
    typedef boost::date_time::c_local_adjustor<ptime> local_adj;
    ptime adjusted = local_adj::utc_to_local(tweetTime);
    std::cout << "Adjusted for time zone: " << adjusted << std::endl;

    ptime now(second_clock::local_time());
    time_duration elapsed = now - adjusted;
    std::stringstream elapsedString;
    if (elapsed.hours() < 1)
        elapsedString << elapsed.minutes() << " minutes";
    else
        elapsedString << elapsed.hours() << " hours";
    std::cout << "Time elapsed since then: " << elapsedString.str() << std::endl;
}

The output is

Time: 2011-Jun-09 00:06:02
Adjusted for time zone: 2011-Jun-08 20:06:02
Time elapsed since then: 55 minutes
Press any key to continue . . .

Pretty neat, isn’t it? The code is pretty readable, too. The adjustment I’m talking about is a translation from UTC to my local timezone which is EDT. I have not found a good way to deal with the UTC offset, but from what I can tell, Twitter will always give me UTC timestamps, which is why I just hardcoded +0000 into the format string. I might have to fix this later though.

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