G-d's Shabbat; our Calendar
Of all the details of the Calendar system, the one that boggles the mind is that potential witnesses can "violate" the Shabbat in order to travel to Jerusalem to give their testimony. The Sanhedrin, in charge of sanctifying the months, can "benefit" from "chilul Shabbat" in order to accomplish their goal. 

Notice that "violate" and "chilul Shabbat" were enclosed in quotation marks (inverted commas) because there is really no violation of Shabbat when Halacha allows us or requires us to behave in a certain way.

It didn't have to be this way. In other words, G-d chose to allow for Shabbat "violation"; He could have gone in the opposite direction by forbidding traveling for the purpose of testifying. He didn't allow the building of the Mishkan on Shabbat. (But He did allow, nay require, various M'lachot to be performed on Shabbat in the Mikdash. If G-d could have gone either way, soto speak, then the question for us to ponder is why He chose what He chose. What message was He sending us. For certainly, that's what He was doing.

G-d created the world in six days and rested on the seveth day. Therefore, He blessed the seventh day and sanctified it. No human being was an eye-witness to Creation. Certainly, no one was an active participant in the original acts of Creation. Shabbat is G-d's, and He commanded us to make Shabbat, to keep Shabbat, to honor Shabbat.

With the calendar and the Holidays that flow from it, the story is a different one. We were slaves to Par'o in Egypt. We left Egypt. We stood at Sinai and received the Torah. We were active participants in the whole process that gives meaning to the Calendar. And therefore, G-d commanded us that the Calendar is ours. So much so does G-d want to bring us into a partnership with Him that He will accept our mistakes in sanctifying Rosh Chodesh. The Bat Kol to Rabbi Yehoshua was unable to change the declaration of the Sanhedrin as to when Rosh Chodesh was and which day would be Yom Kippur. G-d emphasizes the significance and value of our setting the Calendar, that He was willing (so to speak) to set His Shabbat aside to allow us to fix the Calendar properly.

It behooves us to accept this special gift from G-d, to use the Jewish Calendar, to know how it works, and to yearn for the restoration of Sanhedrin when we will take charge again.