I have a short article, the title is
What time is it now?
Can I just write
Qué hora es ahora?
Or must I write this?
¿Qué hora es ahora?
Yes. There are no exceptions to the use of the question marks in Spanish. Questions always start with an upside-down question mark (or better called opening question mark) . It is the very first rule.
Son signos dobles, pues existe un signo de apertura y otro de cierre, que deben colocarse de forma obligatoria al comienzo y al final del enunciado correspondiente
Los signos de apertura (¿ ¡) son característicos del español y no deben suprimirse por imitación de otras lenguas en las que únicamente se coloca el signo de cierre:
Qué hora es?
Qué alegría verte!
Lo correcto es
¿Qué hora es?
¡Qué alegría verte!
As an aside: in Windows, you can type this symbols by keeping the Alt key pressed, while typing the following codes on the numeric keypad (normal number keys above the letter keys won't work):
There are a number of ways to type those same codes in Linux.
English speakers generally know that the sentence they are beginning to read is a question, because they have a grammatical form that presents it. For example, here, in the title of your article:
Do I have to use upside down question marks (¿) in a article title ?
In contrast, Spanish speakers recognize the questions only by the intonation of the spoken phrase. We do not have a grammatical indicator to show that we are reading a question.
Therefore, in Spanish we need an orthographic mark that indicates the beginning of the question. If we do not put that mark (and the sentence is relatively long) we understand that it is a question only when finished reading, which implies to stop reading and reinterpret its meaning.
This is important in all written language, including titles, as it allows us to distinguish what kind of sentence is being communicated: a statement, a question, a statement followed by a question, etc.
The name of the symbol is opening question mark; Not upside down question mark.
I disagree with following answer
"In contrast, Spanish speakers recognize the questions only by the intonation of the spoken phrase. We do not have a grammatical indicator to show that we are reading a question."
Since in English the structure of a sentence is different, you know it is a question. In Spanish the same sentence can be a question or an affirmation.
Question: ¿Se fue?.
Affirmation: Se fue.
So yes, we need to use the opening question mark.