Christmas Invasion - just happened to be at Christmas. Plot itself could easily be moved to anytime.
Runaway Bride - Happens at Christmas and has the alien ship mistaken for a christmas star at the end, but the more memorable "event" that it centers around is Donna's wedding.
Voyage of the Damned - uh happens at Christmas. Other than that, the plot is simply the Starship Titanic
End of Time Again happens at Christmas. Christmas isn't the major theme of the episode.
It's actually only in the early Moffat years that Christmas was the central theme of the special:
Christmas Carol
Doctor, the Widow and the Wardrobe
Snowmen
Time of the Doctor - Clara's timezone was at Christmas, but the story wasn't reliant on it and in fact the town being called Christmas felt shoehorned in.
Husbands of River Song not really a Christmas story although it begins at Christmas
I think really for the most part the only Christmas connection is the date within the show, and that's something that's broader than Christmas. A lot of of times if there's a date they make it near the actual airdate, for example Rose takes place in March of 2005, which was near when the episode aired.
I miss Giles.

It was broadcast on Christmas Day.
It was also more light-hearted than regular episodes.
I believe the makers of Only Fools and Horses were the first to realise a Christmas special doesn't have to be set at Christmas or be Christmas themed. This was quite an innovation at the time, because the necessity of making all TV Christmas specials Christmas themed was very limiting and boring.
When RTD announced back in 2005 that a Doctor Who Christmas special
has to be
about Christmas, my heart sank. The show as he'd conceived it was already far too Earth-centric. Now this bloke who could go anywhere in time and space had to be home (ie in England) for Christmas every year too. Not that he ever left.
So this is permanence, love's shattered pride.
What once was innocence, turned on its side.

Didn't have much Christmas in it Wasn't very 'Special' I'm as perplexed as yourself.

I thought the same thing. In fact, at the end when all the people in the city were pointing their camera phones towards the sky, I expected to see something like the Star of Bethlehem (
caused by the ship exploding in space
) - that would have given it the missing "Christmas-y" touch. Instead we got
Grant holding up the ship by one hand
. Camera-worthy, but not in the holiday spirit.
On IMDb, nobody knows you're a
(I said nobody knows!)
.

Well he wasn't dressed as Santa but he still got mistaken for him and even got a cookie lol

It was aired on Christmas if you didn't notice. Should the Doctor have been dressed as Santa for it to be enough christmasy or what?

Little Grant's parents assumed that The Doctor was Santa Claus and allowed Grant to let him into the apartment. That was the only Christmas reference that I noticed.
Frankly I'm kind of glad it was, they've tried to shoehorn in so many Christmas themes into a story even when it didn't make much sense.

Umm no it really wasn't there was a small Christmas bit at the beginning with the antlers and carol singer joke and the darilium bit was set on Christmas Day that's it. So out of 60 minutes there was probably a total of 5 minutes if that of Christmas stuff

What are you talking about? Husbands of river song was about as Christmas as you can get.

They don't have to be. They are just a special that airs on Christmas. End of Time and Husbands of River Song weren't very Christmasy, and many of the others just kind of had Christmas themes tacked on and didn't really play into the plot liek most of Tennant's specials and Time of the Doctor could have removed all Christmas elements and not changed teh plot at all.