Originally Posted by
halamadrid
Now to answer your question, membership goes by calendar year so if you are trying to qualify for platinum (or maintain gold) you need to complete the required activity before the 2019 calendar year ends.
If you look at what you quoted:
Originally Posted by
kitbag1984
But not sure when the membership year expires [my highlighting]
It usually expires at the end of the calendar year, yes. But there are exceptions (for instance, due to status match promotions or due to the shifts to the membership level duration due to Ambassador).