〜っけ

明日だっけ？

Ashita dakke?

It is tomorrow, right?

っけ checks a memory, with yourself or someone close — never formally

あの人、名前は何だっけ。

Ano hito, namae wa nan dakke.

What was that person called again.

The verbal tic of losing a name mid-sentence

ナ形容詞と名詞には だ が入ります。

Keiyō dōshi to meishi ni wa da ga hairimasu.

A na-adjective or noun takes だ.

休みだっけ is right; 休みっけ is not said