in/on with dmy dates

When writing dates in prose in the dmy format (29 March 2014), is the correct preposition "in" or "on". I'm seeing it with "in" here, but that construction is foreign to me.

It was released in 29 March 2010 on Steam for Microsoft Windows, and in 25 March 2010 on Xbox Live Indie Games for the Xbox 360.

"On" would seem to make more sense, from what I know. Verdict?

On is the only correct preposition here. In is not used to indicate a specific date, no matter what the format.

If you look at the edit history of the Wikipedia page, though, you’ll see that there was originally no date. It originally read:

It was released in February 2010 for Microsoft Windows, and in March 2010 for Xbox Live.

Since this is not a specific date, but rather a period of time, in (meaning ‘during the course of’) is the correct preposition in the original text.

Someone later added the dates and forgot to change the preposition. The user who added the dates speaks Spanish as his first language, a language that makes a similar distinction; so it almost has to be an oversight. No other changes were made in the edit that introduced the dates, so it was probably just a quick’n’dirty fix.