Various verbs such as, cree, saber, pensar, tener, poder, deber, sentirse, necesitar are generally used in the imperfect tense. These verbs in most situations suggest a condition or a state of mind that already existed at the time in question rather than something that took place or began to happen at a particular point in time.
Notice the following differences en the English translation:
saber: No sabía eso antes; lo supe anoche. (knew; found out)
conocer: Yo no conocía a su tía; la conocí anoche en la reunión. (knew; met)
querer: Ayer quería ir al cine e invite a mi esposa, pero no quiso ir. (wanted); refused (negative)
Haber:
Había mucha gente en la fiesta. (There was / were present)
Hubo un terremoto ayer. (There was / were = these occurred)
Some verbs are used only in the imperfect when indicating past time.
ser in telling time - Era la una cuando llegué.
acabar de - Acababa de llegar cuando entró María.
decir - for anything printed or written – El telegrama decía eso.
estar – estuve when duration of time stated; otherwise, estaba
Imperfect indicators are words or phrases that in some way indicate repetitive or habitual actions in the past. Generally, they will be followed by the imperfect tense.
Review the three sets of expressions on the left which are generally associated with the Imperfect tense.
When you begin a sentence with any of the expressions below you will usually need to follow with the imperfect past rather than the preterite past.
por regla general
in general
por lo común
in general
por lo general
in general
a veces
sometimes
día a día
from day to day
muchas veces
many times
raras veces
rarely
cada año
every year
cada día
each day
cada mes
each month
cada verano
each summer
cuando
when
de vez en cuando
from time to time
a menudo
often
siempre
always
todas las semanas
every week
todas las primaveras
every spring
todos los lunes
every Monday
todos los veranos
every summer
cuando niño
as a little boy
cuando niña
as a little girl
cuando ____ era niño
when ____ was a little boy
cuando ____ era niña
when ____ was a little girl
cuando ____ era más joven
when ____ was younger