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):
On Mac, these can be typed with the Option key:
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.
Let me give you an honest answer as a native speaker on both languages.
Though it is grammatically incorrect to ask a question in Spanish using only the closing question point (?) it is common to only use one.
We can relate back to that with something that is nowadays almost universal for languages using the Latin alphabet: the period at the end of sentences. Do you usually end every single phrase you write in English with a period? While the answer may be yes for some people, for a lot other it is 'no'; and even for a lot of people with very good grammar and spelling that is the case.
Coming back to Spanish, the same thing happens. Not all of us use a period at the end of all sentences all the time, nor do we use both exclamation points for questions. It's what's called a linguistic quirk (vicios del lenguaje), and I believe (I really can't 100% confirm this) it actually derived from English.
So, the same way some phrases are grammatically correct but they sound too textbook, using both question points can sound too textbook depending on the context, and may sound unnatural. Knowing when to use both and when to use one is a very blurry area, but (mostly) you should use both on formal settings and only the closing one on colloquial settings. (it is up to you to always use both, anyway)
Long answer I know, but I wanted to be thourough.