Certainly: when reciting days of the week, or a specific day (such as in a timestamp), one form is used - for instance, Monday is "Dé Luain", Tuesday is "De Máirt". But when mentioning days in a general or habitual sense (such as, "databases backups occur on Monday", "Today is Monday", a different form is used - Monday is "an Luan", Tuesday is "an Mháirt".

Thanks for replying, but to rephrase - what question string does this answer string serves as the response to? Irish has no words for yes or no, so the translation of the answer very much depends on how the question was phrased.