Contributions are deductible in the year they are made. Thus, donations charged to a credit card before the end of 2016 count for 2016. This is true even if the credit card bill isn't paid until 2017. Also, checks count for 2016 as long as they are mailed in 2016.
That means that today, is your last chance to front load your giving as experts are recommending. Go to Charity Navigator now to find a charity you can trust and use our Giving Basket to make your donation before the day ends.