boost::gregorian::date does not have `set-type` functions?

Question

For example I have a date object:

boost::gregorian::date date1(2013,1,31);

Now I want to change the day to 1. How to set day to 1?

Answer 1

Date types are immutable, apart from assignment, so you need to make a new date:

date1 = boost::gregorian::date(date1.year(), date1.month(), 1);