Originally Posted by Iceee
Yes you can, although commonly people say "Eid Mubarak" after Eid salah. But this is just a custom.
Originally Posted by Muslim Woman
In Islamic Qomariah (lunar) calendar, the day is not started from midnight to midnight like in Gregorian calendar, but started from maghrib (dusk) till maghrib. So if Eid day is tomorrow, this magrib is already 1st Shawal.