Many of the mitzvos associated with Pesach revolve around proper timing. There are very specific guidelines of time that govern the proper observance of the Korban Pesach. The korban must be offered during the afternoon of the fourteenth day of Nissan. It is critical that it be eaten at the proper time. The precise time for eating is a dispute whether it is until midnight of the fifteenth of Nissan or until the morning. If the korban was not completed at the right time, the leftover meat becomes disqualified, subjecting one who eats it to the severe punishment of kares.
Similar to the requirement of eating the Korban Pesach at the correct time, there exists an obligation to perform the other mitzvos of the Seder at precisely the right time. Tosfos (Pesachim 99b) observes that unlike Shabbos and other yomim tovim when it is permissible to eat the meal earlier than when it is actually nightfall, the matzah must be eaten after dark. By whatever time the Korban Pesach must be completed so too must the matzah be eaten. The poskim extend this insistence on proper timing to the maror, the telling of the Hagada, the saying of the Hallel and the drinking of the four cups.
The basic difference between chometz and matzah is also a function of time. Exactly the same ingredients of flour and water make up both. It is only the factor of time that differentiates between them. Even the prohibitions of eating and possessing chometz revolve around the clock. At one moment in time of Erev Pesach, one can no longer eat chometz. An hour later, one can no longer benefit from chometz. Finally at noon, the prohibition of owning and eating begin according to the Torah itself.
More than any other yom tov, time plays a critical role in the proper observance of Pesach. What is the significance of this? Why does the proper commemoration of Yetzias Mitzraim require such observances that are so time oriented?
During davening and kiddush of each yom tov we mention that we celebrate these days as a remembrance of Yetzias Mitzraim. Although the Shalosh Regalim are linked to Yetzias Mitzraim historically, what is the connection between the observance of Rosh Hashana and Yom Kippur and Yetzias Mitzraim? Even though there is no historical connection, we declare that these two Yom Tovim are also "zecher leyetzias mitzraim." Apparently there is a dimension not dependent upon historical events that link the entire concept of yom tov to Yetzias Mitzraim.
The first mitzvah given to the Jewish people as a nation as they are about to leave Mitzraim is Kiddush Hachodesh - sanctifying the new moon. Is this just a necessary prerequisite since one cannot observe Pesach on the fifteenth of Nissan if Rosh Chodesh Nissan is not declared? Apparently, there is a greater significance why we were given Kiddush Hachodesh on the eve of attaining our freedom. There is one feature that truly demarcates between a slave and a free man. A free man is master of his own time whereas a slave's time belongs to his owner. The halacha teaches us that one cannot sanctify an object he does not own. Not only is this true of material possessions but it is true of time as well. Before the Jewish people were freed it was inconceivable that they should be able to sanctify Rosh Chodesh. The mitzvah of Kiddush Hachodesh was the beginning of the transformation from slavery to freedom. The very observance of yom tov is a testimony to Yetzias Mitzraim. The ability to create "kedushas hazman" of Rosh Hashana and Yom Kippur is a declaration of "zecher leyetzias mitzraim" even if there is no historical connection between them. The relationship between time and freedom is highlighted by the statement of Chazal that only one who is involved in Torah study is truly free. Talmud Torah is a mitzvah that has no limitations of time. One who fulfills this mitzvah properly by salvaging every moment is truly in control of time and is a free man. One who wastes the most precious gift of time by not sanctifying it properly cannot be called a free man.
The celebration of Pesach centers on time more than any other yom tov of the year. It is specifically at this time, when we commemorate our transformation to becoming free men, that the sanctification of time becomes a primary theme of the yom tov. We who now are in control of time can use time properly in the service of Hashem. As we observe the mitzvos of the Seder in their proper time and are careful concerning the prohibitions of chometz we are declaring that this is the celebration of "zecher leyetzias mitzraim."