Thoughts on the day and time

Lee's post about the date of her mother-in-law’s yahrzeit reminds us that marking the dates of events is less simple than it seems. In Lee's case, the Hebrew calendar sets the start of a day at sunset of the Gregorian day's previous evening. Not only that, but holidays seem to float when viewed from the Gregorian platform, but are fixed within the Hebrew view.
What is it that Einstein said, that time is relative from the perspective of the observer? (See Einstein's Time - by Peter Galison for some more discussion on this.)
Even among the goyim, birth dates can get confusing. The shift from the Julian to Gregorian calendars resulted in changed birth dates for our nation's founders - What's Benjamin Franklin's birthday?.
Russia was still on the Julian Calendar in 1917 when the The two-part Russian Revolution. So, the famous February and October revolutions took place in March and November, respectively, according to the Gregorian calendar.
Many Eastern Christian churches still use the Julian calendars for their holidays, so Christmas typically falls on January 7 (Wikipedia on Christmas).
During the run-up to the Year 2000, people started to wonder if their had been similar millennial panics as the western world neared the year 1000. Several historical articles showed that people in those times were more likely to note the years during the reign of a particular king or some other scheme (The Popular View of the Year 1000).
So, our notions of the passage of time get all bollixed up. One of the standard tests that psychiatrists and psychologists use to measure cognitive ability and, well, how in tune with reality a patient might be is to ask, "Do you know today's date?" On a few occasions, I've digressed on the topic of calendars, the relativity of time, and such, but generally, now, just say, "It's Friday, March 5, 2010." (Assuming that they'd be asking me today.) Doctors and others like the answer that they expect

Oh, and don't get me started on Daylight Saving Time.