Prince Philip celebrates 98th birthday

Prince Philip is celebrating his 98th birthday today in private as royal members of the family congratulatedQueen Elizabeth's husband on social media.

In a tweet Monday, the Royal Family wished Philip "a very happy" birthday.

The British army plans to fire gun salutes in Philip's honour. The army tweeted it is "determined to make it a good one."

Some of Philip's children and grandchildren also posted tributes.

Philip has officially retired from public life, although he is still occasionally seen with the Queen at official events. He skipped U.S. President Donald Trump's visit.

The Duke of Edinburgh still drives a horse-drawn carriage on private grounds from time to time, but has stopped being behind the wheel of cars since a serious accident in January. He has also given up his driver's licence.