Psalm 81:1-4
81 Sing aloud to God our strength;
Make a joyful shout to the God of Jacob.
2 Raise a song and strike the timbrel,
The pleasant harp with the lute.
3 Blow the trumpet at the time of the New Moon,
At the full moon, on our solemn feast day.
4 For this is a statute for Israel,
A law of the God of Jacob.

Do you celebrate it for 2 days?