When was the work for the Mishkan completed?
Hadar Zekenim, Ba'al ha'Turim: On the 25th of Kislev. 1
Hadar Zekenim (25:8, citing a Midrash): Chanukah (i.e. Kislev 25) was complaining that the Mishkan should have been erected then. Hashem repaid it, and a miracle was done for Yisrael [on that day, at the time of the Chashmona'im]. See also Ba'al ha'Turim.
Here it says "va'Techal". Why does it say about [completing the work for the Beis ha'Mikdash] "va'Tishlam" (Melachim 1:7:51)?
Riva citing R"M of Kutzi: The Mishkan was finished (erected) in Nisan. Tishrei was complaining that nothing was done in it. Hashem promised it that the work of the Mikdash will be completed in Tishrei. Va'Tishlam - Hashem's vow was fulfilled.