Postmark Picks: Date Formats

Considering the 150+ years of postal history and the 200+ postal authorities across that timespan, and the upheavals of history and war, and cultural/local differences, you should expect postal markings to have a lot of variation around the globe.  This has fascinated since my Dad first got me interested in philately 53 years ago.

My career has been in programming and database work, so I often see date formats in terms of computer codes and international standards.  The most well known variation in date formats is how the American MM/DD/YYYY (month/day/year) format differs from the European DD/MM/YYYY (day/month/year) format, so November 2,2025 would be 11/2/2025 here and 2/11/2025 in most other countries.

Let's get some date codes listed:
M = month (one or two digits)
MM = month (two digits, leading zero if needed)
NN = month name, 2 letters
NNN = month name, 3 letters
R = month (Roman numerals)
D = day (one or two digits)
DD = day (two digits, leading zero if needed)
YY = two-digit year
YYYY = four-digit year
YYY = three digit year, believe it or not, found on postmarks of Hungary from 1890s-1910 or so.
Other punctuation can be included in the format string.  And it feels customary to use a slash / to represent line breaks.

Here is a rare but clear example of DDMMYY from Liverpool:

The "5 A" looks like a time code to me.  These time codes have a variety of formats of their own:
H = hour, 1 or 2 digits
HH = hour, 2 digits padded with 0
MM = minutes, 2 digits padded with 0
A = A/P for AM/PM
AA = AM/PM

Here's a HAMBURG DD.M.YY.H-H.

I find it most clear when the Roman numeral is used for the month, so the day and month are immediately separated stylistically.  Here is a DD.R.YY.-T from Switzerland.

Here is a lovely example of D- R.YY from Viborg:

And a DD.R.YY-- from Tunis.


Here is a neat batch of postmarks on a single cover:

Lexington is MMM D / HMM AA / YYYY
The two London marks are HMM AA / MMDD / YY.


This one from Hamburg has a bit of a twist:

It's HAMBURG / 12 / 20 9 / 00 / 7-8, where the 12 looks like a district number, since the rest covers the DD M / YY / H-H of the date and time.

Early Sweden postmarks have an odd design choice where the year is split to left and right of the DD/MM.

These two cases show that if the month and day values are both 12 or less, it's not clear which is the month and which is the day.  10/7 could be October 7 or July 10.  If this 1875 Stockholm cancel said 28/7, then it could only be July 28.  You can maybe find other examples of the same style of postmark where one of the numbers is clearly the day, but it's still no guarantee that the one you're comparing it to has the same number order. 

There are a lot more varieties to talk about, but I wanted to get the ball rolling with these.  And for fun, here's a case where Elkhart, Indiana appears to have its own set of rules:

Why is the date split up this way??  The date has the month at the top, day at center left, and year below that.  It's NNN / DD   H-MM A / YYYY.   I have never seen anything like this