von heute auf morgen
Literally: “from today to tomorrow”.
- (idiomatic) within a short period of time; overnight; suddenly
- Er hat seine Meinung von heute auf morgen geändert.
- He changed his opinion overnight.
- As seen in the example sentence, the phrase is generally not changed when referring to the past. While it would be grammatically possible to say von gestern auf heute (literally “from yesterday to today”), this would imply that the change actually happened, or was made known, on this very day.