I made a date to go out to diner with a group of friends tonight (Friday) & I don't eat fish due to allergies, not realizing, it was lent. Can I eat chicken or meat without committing a mortal sin ?
Then break the date! Whether it is a mortal sin or not (and it is) what matters most is that the Lord deserves our accommodating our lives for Him who certainly accommodated His for us.
Lent is a time of sacrifice. This is a sacrifice.
Fr. Vincent Serpa, O.P.