The intention of the fast day is the good outcome of the election of a pope.
From the circular letter to the brothers in the German district:
Stuttgart 9, March 2013
According to information from the Rome conclave begins on Tuesday, the 12th March. In order for all the communities of the Society in the German district of Monday or Tuesday to hold a day of fasting.
All the faithful are invited to join in this day of fasting.
On Tuesday, the "Votive Mass for election of a pope" can second classed as a votive Mass in red with Gloria, but no creed, and the commemoration of Lent.
With fraternal greetings,
Father Franz Schmidberger
Note: A fast day is completed according to the Catholic Church's law on a day in which you are taking only one full meal (preferably lunch). In the morning and in the evening just a little snack is allowed (in the morning a piece of dry bread and drink, dinner a bowl of soup with a piece of bread). Drinking does not break the fast.
Under the new Code (1983) obligatory fast days are Ash Wednesday and Good Friday ( this is unknown to many Catholics due to the lack of preaching in parishes!).
The SSPX fasts in their homes, every Friday during Lent and the Ember Days.