I re-encountered this strip
While silly, it makes an important point. For magickal uses, you *don't* go by clock time, nor by the calendar. You go by the sun, the moon and the stars.
If something is supposed to be done at midnight, that means the point halfway between sunrise and sunset *not* midnight by the clock. Note that the difference depends on your longitude (time zone times are only "correct" for a particular line of longitude somewhere in (or near) the zone) and the time of year..
Likewise "noon" is the local solar noon (point when the sun is highest in the sky. This too varies from "noon" by the clock depending on longitude and time of year.
Phases of the moon are more obvious, and hopefully, if your calendar lists moon phases, it gets them right. Still it pays to check as the exact time may place it a day ahead or behind the calendar due to your location.
Yes, the full moon is at the same "time" (UTC) for the entire Earth. But which day that is depends on where you are. There are a number of websites that list the phase of the moon over quite a period.
The equinoxes and solstices are "fixed" (they are when the earth hits particular points in its orbit), but they aren't always the same date on the calendar (that's because the year is not exactly 365 days long, but 365.242... days long). The cross quarter days are the points halfway between them. All 8 are easy to determine with something as simple as a set of sticks or stones placed to line up with sunrise (or sunset) on those particular days. You only need 5 markers because the markers for equinoxes and the cross-quarter days on either side of them get used twice each year.
The actual dates for the cross quarter days tend to be several days off from the dates many pagans celebrate them.http://www.archaeoastronomy.com/
has a nice display of them. Note that all dates are for the *next* occurrence.
Note that (for example) Samhain is actually on N0vember 7th (GMT) this year, *not* Oct 31st!
Some grimoires specify things by the rising, setting or meridian crossing of specific stars. Always double check to make sure that the star mentioned has been properly translated. There are some star names that apply to *multiple* stars at quite different places in the sky.
For writers, this means that details aren't what you'd assume. Also, it offers lots of room for "fluffy bunny" pagans to make major mistakes in rituals. :-)
Another pitfall for writers is that the calendar has changed a number of times over the centuries. First when Julius Caesar fixed the months and set the "leap year every 4th year" rule (Julian calendar), and then later when the current leap year rules were setup by Pope Gregory (Gregorian calendar). There have been other changes, but those are the biggy for the calendar we are most familiar with.
Note that due to the Reformation not everyone accepted the Gregorian calendar at the same time. since part of the switchover involved subtracting 11 days (to get the solstices and equinoxes back on the "right" date, this meant that crossing a border could change the date by 10 days!
That was in 1600. in 1700 it became 11 days. In 1800 it became 12 days. And in 1900 it became 13 days.
And some nations did really weird stuff when they changed over. Check the Calendar FAQ
for *some* of the gory details.
Britain and its possessions changed over in 1752. 2 Sep 1752 was followed by 14 Sep 1752. And I'll just let you check the FAQ for the really convoluted way *they* changed back and forth. I'll just mention that February 30th 1712 was a real date there.
Be very aware of this and other things if you are using astronomical data for the past. It'll be in *Gregorian* calendar form. And sometimes have things like year 0 and negative year numbers (note that -1 is *not* 1 BC)
Oh yeah, the year didn't always change on Jan 1. For example in England it used to change on March 25th. So March 21 would be in one year, but a week later on Mar 28, it'd be the "next" year.
Some of this can be ignored, some can be used for local color.
And since I went into sun & moon based stuff above, one last note. The phase of the moon is due to the angle between the sun and the moon. New moon has the sun and moon at the same angle as observed from Earth. That's why we have solar eclipses then (we don't have one every new moon because the moons orbit i9s tilted.
Half moon has the moon 90 degrees ahead or behind the sun. And full moon is when the moon is 180 degrees from the sun.
Why is this important? Because it dictates what we see from Earth. I've seen cases where a well known author had a full moon high in the sky at sunset. Which is impossible. If the moon is full, it's on the opposite side of the Earth. so as the sun sets, it'd be rising (and vice versa). And the half moon will be highest in the sky at sunrise or sunset.
This stuff will *really* jar a reader if you get it wrong.