Translation:Friday the thirteenth is my birthday.
English used to do this at one time ( reverse the verb so it always becomes 2nd place in the sentence). It exists here-and-there still, for example, as "Hardly had he came when..." and "Sit down, said the teacher!" or "Here comes the bus!" or "Never have so many sacrificed themselves for so few"
if you fancy a bit more on the subject of "inversion" ( I am by no means an expert but have my own way of looking at things and am happy to be told I'm wrong too). The rule to invert the verb and subject if you start with an adverb, or a phrase of time, is simple enough (Tomorrow go-I to town). But you never do it after a conjunction like "and" or "but". Remember that one. There was for me an urge to write " And went I there by bus" or "but liked she not the meal" which took me a time to re-learn was wrong. Also, if the object is a phrase by itself, then it too, isnt inverted... 'I told her, the answer is wrong' ( not "I told her, is the answer wrong!").
I don´t think it will because ¨det/den trettende¨ is in the definite form. It means that the ¨trettende¨ will always be in its plural form, i.e. ends with ¨-e¨.
It always happen for any kind of objective, at least as I have learnt so far, for example:
ugly - stygg (m/f), stygt (n), stygge (pl)
An ugly dog - En stygg hund
An ugly house - Et stygt hus
Ugly Men - Stygge menn
The ugly dog - Den stygge hunden
The ugly house - Det stygge huset
The ugly men - De stygge mennene
This is sort of correct. It's not really the plural form of the adjective, but it's the fact that the definite form and the plural form look the same. In function they are different, though. But yes, this happens with all adjectives. They only agree in gender when it's indefinite singular. So:
et stort hus - det store huset
en stor mann - den store mannen
ei stor kvinne - den store kvinna
en stor kvinne - den store kvinnen)