The construction of the Mishkan was finished on 25 Kislev. Yet, the Mishkan wasn't actually assembled - and the rituals performed - until the first of Nissan.
Immeiately after the construction was finished, everything was brought to Moshe. Shemot 39:36 says that thing included the Showbread (lechem hapanim). Did the Showbread really wait around, uneaten, for over three months?