We got the day wrong!
'Sbagliati' — zba-LYA-ti. The 'gli' makes a 'ly' sound. Stress on the second syllable.
Use when there's been a genuine misunderstanding about which day plans were made for. The plural 'ci siamo' shares the blame between both parties, which is more diplomatic than blaming only one person.
'Sbagliarsi' is the reflexive form of 'sbagliare' (to make a mistake). Using the reflexive 'ci siamo sbagliati' (we made a mistake) is more diplomatic than 'ti sei sbagliato/a' (you made a mistake) and prevents conflict.
Mi sono sbagliato/a di giorno.
I got the day wrong.
Takes personal responsibility — honest and direct
Ho segnato la data sbagliata.
I wrote down the wrong date.
Blames the note/diary rather than yourself — softer option
Pensavo fosse domani.
I thought it was tomorrow.
Simple explanation of the misunderstanding — no blame attached
Schedule mix-ups are common in Italy where plans are often made verbally or through rapid WhatsApp exchanges. Scrolling back through the chat to prove the agreed day is a common (and often humorous) conflict resolution strategy.