'Please pray for me,' pope tweets on first anniversary
Francis uses @Pontifex account during Lenten retreat13 March, 12:45
"Today the pope is not doing anything special or different from other days," Vatican Spokesman Father Federico Lombardi said Thursday. "He is praying".
The decision not to hold any special celebrations is in keeping with the pope's simple, frugal style.
The former archbishop of Buenos Aires has shunned perks and pomp since being elected and repeatedly called for a "poor Church", earning plaudits for attempting to follow the example set by the saint Francis of Assisi, whose name he took.
Lombardi said that on Friday Francis will return from the retreat in Ariccia, a hilltop town 16 miles from Rome, by bus - the same means of transport he used to travel there on Sunday.
His election followed the shock resignation of former pope Benedict XVI, who announced in February 2013 that he did not feel fit enough to continue the job.