If you want to make sure your package is delivered on time for Christmas we need to send the package some days or weeks before, but what if your missionary receives the box before Christmas? 
 
We can fix that by adding a colorful sticker to the box with the message "Do Not Open Until Christmas!"
 
This is optional because, in some cases, you would desire to give the chance to open the package before. 
But if you want him/her to wait until Christmas day, this is the best option to achive your goal!