Question: Why is Kiddush Levana, which is said every month sometime during the first half of the month considered a time bound mitzvah that women are exempt but birkas hachama which is said every 28 years is not considered a time bound mitzvah so women are obligated in saying that bracha?
A. Every 28 years the sun begins its spring season on the eve of a Wednesday, at the same moment when it was emplaced in the cosmos. So in a sense, that rare Wednesday is an anniversary of sorts, a milestone that reminds man of the G-D who created him, his sun, and his earth. (Overview in Artscroll series Birchas Hachamah)
B. Kiddush Levana is the prayer said on the new moon. Which can be said anytime in the evening when the moon can be seen from 3 days after the molad, according to Ashkenazim, or 7 days after, according to Sephardim, all the way till about the 15th of the month, each month.
C. Wearing tefillin can technically be done whenever you want but the mitzvah is only during the day therefore it is time bound. One can sit in the Sukkah whenever he wants but there is only a mitzvah on Sukkos therefore it is timebound.
Answer: The actuality of the sun being in the same spot as where it was from the beginning of time has nothing to do with time, it just happens to be in that same spot at that time period. But the moon, even though it’s found in the sky all the time, we only say a blessing on it the first half of the month, therefore it’s blessing is dependent on time.