What I’m wanting to do is to choose an arbitrary period, add it to the current date and feed this into a variable (of DateTime or time_t etc) such that the month, year etc rollovers are taken account of. If I do this with the Adafruit library for example
aday++; now = DateTime(ayear, amonth, aday, ahour, aminute, asecond);
it will be quite happy to increment the day value out to the 100th of the month and beyond without complaining, so adding 7 to the day to construct a variable containing 5pm on the same day in a weeks’ time can’t be done this way (though curiously the unixtime() returned does appear to be correct, so it’s possible I could reverse it back from that).
I’m happy to code around this, but thought it best first to check if it’s already present somewhere.