Date and time can be represented in many ways.
The Romans had a numbering system where letters from the Latin alphabet signified a value. Roman numerals are still used around the clock and many times for expressing a year something is build, written or made.
This year being 2012 in Arabic numerals is MMXII in Roman numerals. Next year is MMXIII and the year after is of course MMXIIII. No wait, it is MMXIV.
The 12-Hour Clock
A day consists of 24 hours. So naturally 5 hours into the day will be 5:00 and 17 hours into the day will be 17:00. But no. Several countries around the world still stick to the 12-hour clock writing 5:00 AM and 5:00 PM. And in most countries verbal use of the 12-hour clock is common.
The American Date Format
A date consists of three elements: Day, Month and Year.
So to most of the world yesterday the 1st June 2012 will be: 01/06/2012
If you insist using an ISO standard, you’ll do it backward: 2012-06-01
However, if you are from the United States, you’ll do it awkward: 06/01/2012
Even if you are a US data quality tool vendor selling to the whole world, you will still do it awkward:
Blog post published 1st June 2012. Flip that date! – as it will be 6th January to the rest of the world.
Best practice will be writing June 1st 2012 or in other way avoiding ambiguity.