This is a question that will only cross your mind if you're about to travel and realize that you have 6 months or less left on your passport. This happened to me once years ago when I was bound to attend a forum in Malaysia! Apparently, there is a 6 month rule most countries so I freaked and obviously got an express application for the trip.
This time, it happened to Sar. He realized over Christmas that he had 5 months left on his passport when we were meant to travel to Singapore for my brothers wedding. We spent days googling and freaking out over the fact he may not be able to travel. We called the ministry of foreign affairs in Singapore and they tried to contact Singapore immigration but no one could give us a straight answer! Sar went to the Greek consulate in Dublin to apply for a passport and got a letter to show as proof for travel.
We did not want to lose our flight money so we went ahead and traveled to Singapore with our fingers crossed hoping no one would stop him. The thing is we had two stops.. one in Amsterdam and China so the chances of getting stopped was high. True enough, we got stopped in Amsterdam and it was not pretty! They refused him to board and we were surrounded by staff telling us there was no way Sar was getting on the flight. Here is when I tell you.. PLEASE MAKE SURE YOU HAVE MORE THAN 6 MONTHS left on your passport. Our story was probably an exception.
Good news is, I insisted we speak to the airline manager and after much crying we convinced her that we had to board the flight. She made Sar sign a piece of paper to say it wont be the airlines fault if he was refused entry in Singapore. We had no problems in China though! So, here is a tip for you, if you would like to increase your chances for entry maybe prepare all your documents in hand (especially if you are travelling for an important event). In this case we had my brothers wedding invitation, passport application letter and proof of our relationship status. THIS DOES NOT GUARANTEE entry but it may help like it did in our case. Singapore immigration warned Sar and told him not to do this again so I guess moral of the story is to be on top of things. It would be shitty to be travelling towards a sunny destination and get turned away back to the cold.