1. was it?; I think it was ...; if I've got it right; if I'm not mistaken; remind me; tell me again
used when trying to recall something or to ask for confirmation
あれって、いつだっけ。When was that again?
2. (I, we) used to ...; I remember ...; it was ...
expresses nostalgic recollection
初めて会ったのも、こんな雨の日だっけ。The day we first met was a rainy day like this one, too.