My sister and I are trying really hard to find out the name of a movie we watched as kids. I think it was made in the 70s or 80s. The movie is about two sisters who get lost in a forest somehow. It's live-action and animation and very surreal. It begins with the sisters playing in a field, and they are drawn to a creek where they find a frog who they begin to follow to the forest. Father Time has cast a spell that makes the forest winter forever, and the girls are in search of Mother Nature (or Mother Earth?) to bring the four seasons back to the forest. In the end, they wake up and realize it was a dream, and the actors who play Mother Nature and Father Time turn out to be their parents. We have been trying to remember the name of this movie for years now. If you remember it and can even just acknowledge that it exists, we would be grateful! If you know the name of it, we will be eternally grateful and this mystery that has been haunting us can finally be laid to rest. Thank you.

Sounds very much like this:
Maria, Mirabella (1981) - IMDb

Here's the full movie - with subtitles (I think?) I watched a few minutes of it - odd!
https://www.youtube.com/watch?v=3vcDG_Ha0hY

This is it!! Wow, thank you SO much! I can't begin to explain how grateful my sister and I are for this. We were starting to think we had both imagined it!

Great :)

You really must be an expert! What an obscure and strange movie. I think we must have watched a version with an English dub. Have you seen it before, or were you just familiar with it somehow? And if so, how did you know about this movie? It seems like the type of film someone might only come across by chance. Word of mouth doesn't seem likely because it's not actually a very good film (lazy ending, etc.) and it appears like it was made on a low budget, so probably released with little publicity. I'm shocked. I've never talked to anyone else who's even seen it, much less known the name of it. Thank you, thank you, thank you. I'm so excited to watch this again with her.

I'm so glad it's the one you were looking for! Thank you for coming back to let the site know. I had never heard of or seen this film. I find myself quite successful with search word combinations, then I spend time and weed through anything that looks like it might possibly be what I'm looking for. There is so much information out there, it can be very overwhelming if your search words are too broad (like: kids movie with sisters), but at the same time, if you are too precise with your search words (like: movie girls find frog), you could be limiting your results, especially if what you remember is incorrect. What if the 'frog' was really a duck? Memories can be a funny thing.
What I did to find your movie is start with: movie live action animation. I was able to find from there a page that had 50 or so movies listed and I went through them, checking the dates first (you said 70's-80's) and kind of just going by the title to see if it sounded like a children's movie. If it did, I wrote it down then after I had like 3 or 4 possibilities I looked them up. Yours was the first one I checked. :)