1. Question: According to the opinion brought down in the Minchas Chinuch (mitzvah 423) that if you fix tzitzis at night on a day time garment which one corner broke, it is invalid and must be restrung in the day because the night isn’t a time of performing the mitzvah of wearing tzitzis but why then can you bake matzah before Pesach or build a Sukkah before Sukkos?
A. The issue for not working is the concept of “ta’aseh vilo min ha’asui” which means that there has to be an obligation to do the mitzvah ready to be when you set it up, not set it up beforehand then the obligation comes in. For example you can’t take a rounded garment, which doesn’t have an obligation of tzitzis and put tzitzis on four sides and then cut out four corners so that it would now be obligated in tzitzis after the tzitzis was tied on.
B. What obligates a garment in tzitzis is a four-corner garment but the obligation is only during the day according to most opinions.
C. There is a difference between a passive exemption and an active exemption.
Answer: By tzitzis the exemption of night time is actively exempting one from a potentially preexisting obligation, therefore the concept of taaseh vilo min ha’asuy kicks in because there is an obligation that can be fixed so it has to be fixed when the time is appropriate but by shofar and sukkah there isn’t an obligation before the Yom Tov so passively time just happened to not cause the obligation to kick in but since it is not actively stopping it then preparations can be made to prepare for the mitzvah to take place when the time comes for the obligation to kick in.