If they have the same meaning and usage, there’s probably negligible difference. Probably just depends which you feel like saying.

@Astralfox: I actually tried おなじ first, but I think I pushed “down” instead of “space” and that’s why it didn’t show up. I think I’ve only just realised that space gives you a list of kanji while down gives you a predictive text feature >.<

@Pindy: I think Joel’s method is good, typing 日々（ひび）then deleting the 日. I’d do similarly if I want to type a single kanji that doesn’t appear as a word by itself, like writing 濯 via 洗濯機.

Here’s a (kinda) relevant link: http://www.hadamitzky.de/english/lp_special_chars.htm

For some reason, there’s no 々 listed there, but when I went to copy and paste the mark for this post, Rikakun gave me the reading (among several) のま, so when I type that in it’s one of the first options. That’s in the Google IME, but it might be similar for other IMEs.

Why is the title “militaristic”? “…doesn’t seem to apply to this characteristic” – what do you mean?

@vanandrew: http://www.alc.co.jp/
It’s all in Japanese, but all you have to do is type the word in the box (Japanese OR English, I think) and hit enter. Lots of good example sentences. From what I’ve heard, it’s a good resource for translators since… well, it’s probably easier if you just try using it and see what it’s like :D

Looking it up on ALC, they’ve translated 「～するはずだった」as “be supposed to”, which is a common thread of most of their examples. When it comes down to it, it’s just the past of having an expectation of the clause before it, to have been sure that it was going to happen, so “be supposed to” is a nice, natural way of saying it in English; that must be a common translation, I’m guessing.

I’d say that  “すし　を　たべる　はず　だった.” means “I was supposed to eat sushi”

ALC has 「～するはずだ」as being “be expected to”, which when you compare it with the past form mentioned above makes sense. If it ends with だ, there is a current expectation that said thing will happen, while if it ends with だった, sometime in the past there *was* an expectation for events to turn out that way.

As for  ”すし　を　たべた　はず　だった”,  to be honest, I’m not sure. There really aren’t many examples  on either jisho or ALC. While there were no examples on jisho that had BOTH past forms at once, all the (four) examples with the first part past and the ending non-past have as translations things along the lines of “should have” and “ought to have”, so maybe you can extrapolate from there. It really doesn’t look that common a construction.

Not a definitive answer, but hopefully it helps and/or someone else can shed some more light on it :)

My advice? If you think it might help, try it :)

Personally, I have my cards going from Japanese to English, but other people have it the reverse (and I’m sure others have both, or change every so often); there are benefits and drawbacks to both.