Another common use of Haver is to indicate that an amount of time has passed before the present moment. It roughly corresponds to the English adverb “ago”, or to other expressions which signal that a certain measure of time has passed.
When used in this way, Haver is only conjugated in the third person singular, “há”. This is known as Haver‘s “impersonal” use: the verb doesn’t have a specific subject, so there are no other conjugations. Let’s have a look at how it works. Examples:
As piscinas fecharam há cinco minutos. 
The pools closed five minutes ago.
Há muito que não comia panquecas assim. I haven't had pancakes like those in a long time.
Estou à espera do cartão há seis meses. I've been waiting for that card for six months.
Similarly, Haver can be used to ask how long something has been going on for. Examples:
Há quanto tempo estás à espera? How long have you been waiting for?
Está a chover há muito? Has it been raining for long?
Notice that “há” by itself means nothing – it always requires a quantifier (muito, pouco, algum, etc.) or a specific amount of time (seis minutos, dois meses, vinte anos, etc.).
