C++ How to get the Day as a number from BOOST localtime

Hi there,
I want to get the day as a number from:
boost::posix_time::ptime today = boost::posix_time::second_clock::local_time();

(i.e, I want to get day of week 0-6 with Sunday==0  )

Thank you.
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evilrixSenior Software Engineer (Avast)Commented:
If you use the to_tm() function you can get the days of the week out of the tm struct.


tm to_tm(local_date_time)
A function for converting a local_date_time object to a tm struct.
// 6am, 2005-Jul-05 local time
std::string z("EST-05EDT,M4.1.0,M10.1.0");

ptime pt(date(2005,Jul,5),  hours(10));
time_zone_ptr zone( new posix_time_zone(z));
local_date_time ldt(pt, zone);

tm ldt_tm = to_tm(ldt);
/* tm_year => 105
   tm_mon  => 6
   tm_mday => 5
   tm_wday => 2 (Tuesday)
   tm_yday => 185
   tm_hour => 6
   tm_min  => 0
   tm_sec  => 0
   tm_isddst => 1 */

Open in new window

tm_wday      // int days since Sunday 0-6

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ambuliAuthor Commented:
Excellent.  Thank you!
evilrixSenior Software Engineer (Avast)Commented:
Thanks, ambuli. It's not the most elegant of solutions but it does work. There may be a better way but the truth is I really don't like the Boost date/time library as I think it's way over-the-top complex for 99% of use cases.

As an aside, if you are using a C++11 compatible compiler you might want to consider using the Chrono library instead. It's quite different from the Boost library and will take a little bit of reading to use it properly but it is way better and significantly simpler to use.

Best wishes.
you could do

time_duration td = today - pdate(date(2015,Jan,4), time_duration(0));
int day_of_week = (td.hours()/24)%7;

Open in new window

jan 4 was a sunday.

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