Possible Clues:

• Old name for the three days before Lent
• The three days before Ash Wednesday
• Shivered, to suffer period that's usual in February
• "Enjoy the merry -- of thy youth!" (Longfellow, The Spanish Student)
• Featured in the Lenten dramas of Hans Sachs
• Converted, he drives to confession at this time
• Herriot, say, needs authentication to invade horse — mad time of year
• To Verdi she represented the period before Lent
• Barge crossing river current in winter days
• Three days preceding Ash Wednesday