[boost] [chrono/date] date conversion and arithmetic with unvalidated dates

Subject: [boost] [chrono/date] date conversion and arithmetic with unvalidated dates
From: Vicente J. Botet Escriba (vicente.botet_at_[hidden])
Date: 2013-05-06 06:30:12

Hi,

Note that N3344 suggest only day arithmetic for a day representation 
(which is always valid) and suggest only only a date representation.

Could we apply arithmetic operations on a unvalidated date (without 
striving on UB)?
e.g. day arithmetic on a ymd_date

ymd_date d1(year(2013), may, day(66));
ymd_date d2 = d1 + day(1);

If defined, which must be the value of d2?

Could we convert a date representation to another one if the source date 
is unvalidated (without striving on UB)? e.g. ymd_date -> days_date

ymd_date d1(year(2013), may, day(66));
days_date d2 = d1;

If defined, which must be the value of d2?

Best,
Vicente