Tenses

I was doing

long action in the past, usaually at same time as past simple

when, while, as long as

I had been doing

action taking place before a certain time in the past, sometimes interchangeable with past perfect simple.

for, since, the whole day, all day

I have done

began in past, still here. effect.

alread, ever, just, never, not yet, so far, till now, up to now

will be doing

arrangements, plans, in progress, action that is sure to happen in the near future

in one year, next week, tomorrow

will have been doing

duration, not finished

for..., the last couple of hours, all day long

will do

spontaneous decisions, prediction, request, offer

in a year, next, tomorrow, probably, perhaps, Conditional I, I think

will have done

result, finished, action that will be finished at a certain time in the future

by monday, in a week

I did

completed action

yesterday, 2 minutes ago, in 1990, the other day