Translating 'For' in Time Expressions

Spanish has several ways in which expressions such as "for three days" and "for six months" can be stated. Your choice of which expression can be used depends, among other things, on the length of time when the specified activity occurred and whether it is still occurring. Although it is possible to translate "for" in time expressions using por or para, those prepositions can be used in time expressions under only limited circumstances.

Here are some of the common ways in which "for" in time expressions can be said in Spanish:

Using llevar: Llevar is commonly used in the present tense when discussing an activity that is still occurring. If it is immediately followed by a time period and then a verb, that following verb is typically in the gerund form (the -ando or -iendo form of the verb):

• Llevo dos meses viviendo en Santa Ana. I have been living in Santa Ana for two months.
• Llevo un año sin fumar. I have not smoked for a year.
• Los perros llevan un mes en una jaulita porque no tenemos otro sitio para ellos. The dogs have been in a cage for a month because we don't have any other place for them.
• Llevamos dos años buscando una casa. For two years we have been looking for a house.

Llevar is typically used in the imperfect tense when discussing the past:

• Llevaba un año preparando su salida. He had been planning his exit for a year.
• Llevábamos un día esperando la mejoría de las condiciones meteorológicas. We had been waiting for a day for the improvement of weather conditions.

Using hacer + time period: The hace form of hacer followed by a measurement of time is commonly used as the equivalent of "ago" in sentences such as this: Hace una semana estudiaba mucho. (A week ago I was studying hard.) But when an hace phrase is followed by que and a verb in the present tense, it can refer to something that is still occurring:

• Hace un año que estoy preocupado. I have been worried for a year.
• Estoy aburrido. Hace tres días que hay poco que hacer. I'm bored. There has been little to do for three days.
• Hace treinta minutos que ya tengo treinta años. I have already been 30 years old for 30 minutes.

Leaving "for" untranslated: When an activity is no longer occurring, the "for" in time expressions is frequently left untranslated, as it often can be in English:

• Estudié dos horas. I studied (for) two hours.
• Vivímos varios meses en Madrid. We lived in Madrid (for) a few months.

The same is true for the future:

• He decidido que estudiaré una hora diaria. I have decided (that) I will study (for) an hour each day.
• Vamos a trabajar un día más. We will work (for) one more day.

Using por: When por is used for expressions of time to mean "for," it suggests a short period of time:

• Presione ambas teclas por dos segundos para enviar un mensaje. Press both keys for two seconds in order to send a message.
• Yo quisiera ir a Londres por sólo un mes. I would like to go to London for just one month.
• No se me pasó por la mente ni por un nanosegundo. It didn't cross my mind for even a nanosecond.

Using para: The preposition para to translate "for" in time expressions is used only as part of a phrase that acts as an adjective:

• Tenemos agua para un día. We have enough water for a day.
• Tengo trabajo para una semana. I have work for a week.
• Un hotel para un mes no tiene que ser caro. A hotel for a month does not have to be expensive.

Note that the para phrase in each sample sentence doesn't affect the meaning of the verb, but rather one of the nouns.