What is the easiest way to make a time limited discount?

In the Educated Singles Club we have monthly and annual recurring memberships connected to stripe payment. That works beautifully.

But as Valentine’s Day is approaching we want to give a 50% discount to all standard members who upgrade on Valentine’s Day.

but how do we do that practically without disturbing something that already runs smoothly. In paid memberships we can make another annual membership with the discounted price, and I haven’t found any solutions for adding a discount or promotion code that gives the 50% discount.

right now we are thinking about just issuing a 50% refund right after s standard member has   purchased an annual membership but that solution won’t win a beauty contest, wouldnt it?

so if you have any ideas, then please share then, soon!

all. The best 

Finn