Where are you seeing that the “posted web site date” was picked up by google’s caching the next day? What evidence do you have that the posted web site date for the fundraising page (December 11) came from a different source than the posted web site dates for the other pages (July, Sept, Oct)?
The dates that show are from the system clocks of the machines that posted the page. They can be right or wrong.
The date on the caches comes from google’s servers, which are most likely exactly correct for the time zone where they are located, like FR’s Dates.