On Saturday evening, April 6th, the new moon was sighted in the western hemisphere, and there was one reported sighting of it from Israel, but there was no second witness. As it was the 29th night, Sunday evening April 7th was declared to be the 1st day of the new month by default.
Devorah’s Date Tree on the sighting of the new moon
Michael Rood on the sighting of the new moon
Hebrew in Israel on the sighting of the new moon
Chag Sameach! (Happy Holiday!)