I am aware of the Between dates. I try to reserve that for those dates that have definite boundaries. ie. the woman appears in the 1860 census and the second wife's first son is born in 1866. Therefore the second marriage probably occurred between 1860 and 1866.
I do not like to use "between" for dates with undefined boundaries.
It would be nice to have a second tag for guesses. ie guess 1850 - 1880