I need info about the 5th Day glitch..
First of all, what is it? And is there any use for it in a speedrun?
If you read the post you quoted you'd have a basic understanding of it.
I don't have the savestates to analyse the glitch to confirm, but basically with MM things work like this:
You have 4 byte day counter. The intended day range is 0-4, where 0 is the day before you enter Termina, 1-3 are your main three days, and the 4th day is the Dawn of a New Day. Normally, even if you get into the 4th day, it's impossible to go farther than that since the 4th day rolls over back to the 4th. When you dupe over the Gibdo Mask and store Hot Water in that bottle, it speeds up time crazy fast for some reason, allowing you to shoot past the 4th day.
Now, to determine what day of the week it is, some things will take the current day variable, divide it by 5, then use the remainder to figure out what the current day is, while others use the day variable as is.
So the 5th day glitch is not necessarily glitching to the 5th day, but rather glitching beyond day 4 to where (day variable % 5) == 1, same thing as the New Day wrong warp.