解决方法
见：
Date/time conversion: string representation to time_t
和：[Boost-users] [date_time] So how come there isn’t a to_time_t helper func?
所以,显然这样的事情应该有效：
#include <boost/date_time/posix_time/posix_time.hpp>
using namespace boost::posix_time;
std::string ts("2002-01-20 23:59:59");
ptime t(time_from_string(ts));
ptime start(gregorian::date(1970,1,1));
time_duration dur = t - start;
time_t epoch = dur.total_seconds();
但是我不认为它比Rob’s suggestion更干净：使用sscanf将数据解析成struct tm,然后调用mktime.
