@Robusto Here is a very good explanation in English of the difference between era and fui (the imperfect and the completed past). The examples are Portuguese, but the same applies very exactly in Spanish. Plus they are very easy and all direct cognates to Spanish and I'm sure you will be able to read enough of them for this to be use to you. The explanation itself is in English.
If you google quando eu era criança/uma criança and quando eu fui criança/uma criança you’ll see that era beats fui 210 to 1. This is partly because quando eu era (uma) criança is more idiomatic, but that’s not all.
The first thing to note is that the absolute length of time an action or state la...
@Cerberus It has to do with whether the speaker is thinking about a time frame that is ongoing or completed. Juxtaposing "when X, (then) Y", the X is usually in the imperfect and the Y in the perfect because Y is an event and X is a durative condition. Think of "when" as working more like "while" in describing an ongoing situation.
It may be useful to look at his very last pair of contrasting examples where either can serve but carry a different meaning.
It's like there being places where both indicative and subjunctive could go depending on the speaker's point of view: they mean something different.
@crl No: I just find it shocking how often I see the wrong plural in respectable newspapers! It's probably because you can't hear an -s in French that uneducated speakers assumed there must be an -s since it is plural.
@Cerberus yes people not familiar with Latin :), but well, I guess in several decades it will be accepted (edit it seems already the case), like forums, post-scriptums have been
@tchrist I guess i have to get accustomed with this English 'way', it's like "He's 12 years old" actually