Pope John Paul II is marking two important dates in the coming days, celebrating his 78th birthday on Monday and, on May 24, becoming the longest-serving pope this century.

By Vatican calculation, he will surpass the 19 years, seven months and seven days served by Pius XII, pope during World War II and until his death in 1958.John Paul's birthday is a regular working day - he will receive the president of Lithuania among other activities. Only a private celebration with friends and close aides is planned, Vatican officials said.

But greetings have been pouring in. During a visit Friday to the Vatican, the king and queen of Belgium wished him a happy birthday and best wishes in advance of the 20th anniversary of his election as pope. That anniversary will be marked in October.

John Paul also is certain to receive lively birthday greetings during a visit to a parish Sunday in a working class district of Rome, part of his regular tour of churches in his jurisdiction as bishop of Rome.

During such a visit a year ago that fell on his birthday, he reflected on his birth in Wadowice, Poland, on May 18, 1920, and said he had begun to approach the "sunset" of his life.

Illness has slowed the once dynamic John Paul. He often uses a cane following hip-replacement surgery; slurred speech and a trembling hand could be symptoms of Parkinson's disease, although the Vatican has never confirmed he suffers from that ailment.

Still, he goes on with his travels, both in Italy and abroad.

He was scheduled to visit Turin, Italy, next weekend, Austria next month and probably Croatia in October. A visit to include St. Louis and Mexico has been confirmed for January.