These options will be used on objects of class 'yearmon'.
opts_yearmon(constructor = c("as.yearmon", "yearmon", "next"), ...)An object of class <constructive_options/constructive_options_yearmon>
Depending on constructor, we construct the object as follows:
"as.yearmon" (default): We build the object using zoo::as.yearmon() on
a string in the format "2000 Q3".
"yearmon" : We build the object using zoo::yearmon() on a double in the
format 2000.5
"next" : Use the constructor for the next supported class.