Possible Calendar Error?

I set my characters birthday to the 28th Day of the 5th Astral moon because that should correlate to September 28th (my birthday), but the date it gives in the character selection screen is 9/27. I'd forgotten all about it, but today I fantasia'd and though I'd find the error.
The 7th and 8th days of that month both read 9/7. Is this an error?

https://photos.smugmug.com/Hosted/n-.../i-8K32QMF.jpg

https://photos.smugmug.com/Hosted/n-.../i-sCWrMPf.jpg


Thanks

There are 32 days per Eorzean month. In order to match with our calendar, two days in a Eorzean month can correspond to the same day for us.
For 31-day month, this occurs only once. For 30-day month, this occurs twice and for February, I think it happens thrice (so that it should be seen as a 29-day month).