i fredags vs på fredag
I'm pretty sure this doesn't come up in the course (not that it needs to— the course covers a lot!) but I thought I'd make a discussion topic on "i fredags".
I had never seen it before, but it means "LAST friday". (And you can also say "i söndags", "i måndags", etc)
What does the extra 's' imply? What other phrases add the 's' onto the end of things? And is the G here silent also?
I don't think it implies much at all, but it's the common way to form references to days or seasons in the near past. It can be just -s, as on weekdays, but it is -as on the seasons.
Examples: I fredags (last Friday), i måndags (last Monday), i vintras (last winter) and i våras (last spring).
Hmm, what is up with this S...
There's also "dags", like "dags att göra xyz" or "läggdags" (such a cute word) which can be in the future...
As for dags, it just means "time [for]" in this sense. I suggest you don't treat its -s as the same kind.
It's an old genitive, which used to be required for certain prepositions such as i. It survives as a fossilized form in certain fixed expressions, such as these. There are also other ones with till, like till sjöss,till salu, till godo etc. i X is just a common expression for referring to past points in time, as "in X" is in English.
In older times still, i took the accusative, which survives expressions like i godan ro and i högan sky (-an marks the accusative).
As for which other expression use i in this way, these are the ones I can think of (some of which have also been mentioned by others):
Referring to a previous time, as in the closest previous instance:
All the weekdays: i måndags, i tisdags etc.
All the seasons: i höstas, i somras etc.
i fjol - "last year". Fjol is a special word that doesn't occur elsewhere.
- i veckan - can refer to the coming week, the current week and (maybe) also the previous week, depending on which tense is used and the context.
There is also a contrast between for example förra måndagen and i måndags for most people. I måndags refers to the closest previous Monday, while förra måndagen refers to the Monday before that, i.e. Monday last week (or two weeks ago if you say it on a Monday). For some people they mean the same thing. In reality, this means only förra måndagen is ambiguous to some extent.
We also have 'i julas' (last christmas) and 'i påskas' (last easter).
The G in 'fredags' is often silent. But not as often as in 'fredag'. If you want to speak proper rikssvenska, you should probably try to squeeze in a small G-sound between the A and the S.
I can't say I agree that it's necessary in "proper" rikssvenska. Perhaps a few decades ago, for news anchors etc., but hardly today. Both exist today and I daresay [fredass] is more common than both [fredaas] and [fredaags] even in more formal contexts.
About the G in Mån-Sön, most people don't pronounce them (at least where I'm from in the north). I say I fredas for example.