fixes for time:strptime

What would be the best way of checking if the day of the week (tm.tm_wday) has been set?
If it has been set we can use both the day of the week and the given week number (%W) to calculate the day of the year.

Having in mind, there are multiple things that could be calculated as well, like month, day of the month, etc

What I've written is a hack to show what I am trying to do, but not definitive.