Is it possible to amend a past year return to use current year's short term gain to cover past year's short term loss?

On last year's tax return I used my long term gain to cover short term losses, and the total capital gain was positive. On this year's return I made short term gain as well, but I have to pay a decent amount of taxes. Is it possible to amend last year's return so that I can use this year's short term gain to cover last year's short term loss, and then I'll pay the taxes for the long term gain from last year?