First, let’s see what both means.
The way of dating history that most are accustomed to see is probably BC (or Before Christ) for everything that comes before the year 0 (zero), and AD (or Anno Domini, latin for “in the year of our Lord”) for everything that comes after year 0 (zero).
BCE stands for Before Common Era, and CE for Common Era. These prefixes mean exactly the same as BC and AD.
So, if they mean the same, why not use BC and AD?
The reasons are simple. BC implies that the birth of Jesus Christ was in the year zero. However, there is no universal agreement on when Christ was born, with theories going from as early as 6 BCE, and as far as 4 CE, meaning the implication of “BC”, or Before Christ is flawed.
Another reason is that Japan uses different calendars than in most western countries. Using the Japanese calendar to explain historic events would confuse most readers, and make it hard to understand from the reader’s perspective. Making use of BC / AD would impose the Christian calendar on a culture in which Christianity has had no impact in its ancient history, and little impact in its more recent history.
It is for these reasons, among others, that we decided to use BCE and CE instead of BC and AD.
This again was a difficult choice to make. While this website has been written entirely in English for now, we hope to be able to translate it in different languages in the future. Thinking of that, as well as the fact that most of the world uses the DMY (Day Month Year) system. In Asian countries, such as Japan itself, it is more common to use YMD. The countries that use the MDY format are: United States , Canada (partially), Belize, Federated States of Micronesia, and the Marshall Islands.
These countries answer for around 360 million people. On the other hand, the number of users of the DMY format are close to 3.6 billion, whereas the number of YMD users (mostly from Asian countries) is close to 1.75 billion people.
This is why we decided it would be better to write dates as “1 January” instead of “January 1” for the English website. If we ever translate the website in an Asian language, depending on the country’s usage, we will probably put the format accordingly, as YMD (or as it is now for Asian countries using the current format).
The main reason is for readability, and to avoid any confusion. While we guess most people would be able to understand the am/pm format, it might be easy to confuse for some people. One of the most confusing times are 12 am and 12 pm. We have noticed that a certain number of people wonder whether 12 am is noon or midnight. This is why we decided for the 24 hour clock instead of the 12 hour clock.
As an additional precaution, we usually write time such as: 03:00 in the morning, or 15:00 in the afternoon. This extra precaution might sound redundant, but this will allow for more certainty, and less chances of readers to mistake the time of certain events.