I am a little confused. Is this present or past? I understand the idea of getting upset in the past, and being upset now as a result of something that happened before, but then how do you distinguish between asking why are you upset now or why were you upset some time in the past? Do you have to add a time-marker like yesterday or last week? I have the same doubt in, for example, устал. (are you tired/were you tired?). Thanks in advance, lingots for help ahah :D :D
The source of your confusion is probably because the Russian sentence should have been translated as 'why did you get upset', whereas the English sentence is closer to 'почему ты был расстроен' in Russian. This is probably due to the flexibility of expression of this both in English and in Russian, but I'd say it's a mismatch here.
It's actually more logical than a lot of other things in Russian.
Think of it this way: you can be in the process of getting upset and you can achieve the final state of being upset as a result. You can be in the process of being upset in the past and in the present (and the future). You can be in the resulting upset state in the past and in the present (and the future, too, of course).
The verb for getting upset is расстроиться (perfective) and расстраиваться (imperfective). The adjective/participle that describes the state is расстроенный (long masculine form, расстроенная for feminine) or расстроен (short masculine form, расстроена for feminine and so on).
Then, all of these correspond to their English equivalents thusly:
- I was upset -- Я был расстроен (была расстроена) [past participle, long form is used less frequently with just он/она/... ]
- I [have] got[ten] upset -- Я расстроился [past perfective, finished the process of getting upset]
- I have upset her -- Я расстроил ее [perfective]
- I have been upsetting her -- Я расстраивал ее [imperfective]
- I was getting upset -- Я расстраивался [reflexive, past imperfective form, not finished the process]
- I am upset -- Я расстроен (for Я, the long form is not used, but for он/она you can say он расстроенный, она расстроенная) [present participle, in the state of being upset]
- I am getting upset / I get upset -- Я расстраиваюсь [currently or generally/habitually getting upset, for instance, "я расстраиваюсь когда ты не пишешь" // "I get upset when you don't write"]
- I will get upset -- Я расстроюсь [simple future tense]
- I will be getting upset - Я буду расстраиваться [future imperfective]
- I will be upset -- Я буду расстроен [future perfective, will be done getting upset and will be in the upset state]
- I will upset her -- Я расстрою ее [simple future tense, perfective form]
- I will be upsetting her -- Я буду расстраивать ее [future imperfective form]
As for time markers, I don't think they are needed most of the time, but that depends on the context a lot. If it's important, you typically say explicitly what you are talking about, if not, you don't. Nothing special about these verbs and time markers, though.
how do you distinguish between asking why are you upset now or why were you upset some time in the past?
For now, it's почему ты расстроен? For the past, почему ты был расстроен. Same for the future, будешь расстроен. Exactly the same as in English: were/are/will be upset. All these ask about the state, not the process, though.
You can also ask the same about the process, почему ты расстраивался (imp past), почему ты расстраиваешься (imp pres), почему ты будешь расстраиваться (imp future). Similarly for perfective verbs.
Hope this clears things up a little, but feel free to ask further.